Nad c-370: Right Channel drops out

What's a 'main amp kit'???

Well, Tbone, I don't know.
RadioShackup has some stuff. Read the label, then the same label at the 'audiophile' shop which will be 5x the cost and probably the same stuff from the same pipe.
Use per directions. I HAVE NEVER USED THIS STUFF, so I don't know any potential downside.
REPEAT:: I have never used this stuff, so read the can. TWICE.

Also, I know it isn't fair, but women STATISTICALLY pay more for cars than men, even comparing identical cars / equipment. So, when they see a woman come in to pick up some electronics, they feel free to BS away, even if it is another woman behind the counter.....Isn't sisterhood powerful?

I don't know current (no pun intended) practice, but large caps come with screw on contacts. These are easily replaced, if they are connector up. Sometimes there is a band around the bottom, sort of like a hose clamp, to keep the caps mechanically secure. After everything has been unplugged for a couple hours, it should be OK to service. WARNING.....WARNING:: Caps typically come with some 'bleed' resistance across them, so they won't hold a charge for long. If these resistor(s) are defective a cap can hold a LETHAL charge for quite a while.
If you aren't comfortable with this procedure, have a REAL tech do it for you.

If you believe in 'audiophile' caps, you can either specify at time of work order, or bring 'em in yourself. Cap size can vary, even for same rating, so be careful there, too.

Now that I've either A) scared you or B) confused you, please feel free to follow Kotta's advice. Probably better than mine!

I know there is sometimes special knowledge involved, but really. Once a tech has the schematic and test values what could possibly go wrong? Mechanical disassembly except in special cases is pretty routine.
The only 'glitch' in the ointment would be proprietary parts / devices or, for example, the 'potted' gain cell circuitry in my PS Audio integrated. I don't see NAD using any such parts or devices.

Any tech should be able to fix a NAD amplifier unless a board has been charcoaled.

Well, as a matter of fact, I've worked on semiconductor processing equipment for decades. I was expected to be able to fix darn near anything, at least to the board exchange level with schematic, knowledge of how it was supposed to work a meter and scope.
What's the big deal? It's just an amplifier.
I know I simplified things, but after all, if you are dealing with a professional analogue tech who is familiar with amps, preamps and can align an FM tuner or use a tube tester (for vets only) I don't really see the problem.
Is how this stuff works a mystery? Do you need to be admitted to some cults inner circle? Is fixing stuff Masonic or Religious?
Nope, it's just electronics.
Sound technique and reasoning will get you thru many fixes with no special knowledge. Maybe not even a third, but you can really fix stuff without resort to dead chickens or tea leaves.

Back to the OP. See where he writes::
'I can get the right channel to come on if I tinker around with the amp by switching source inputs form CD to Video and so on.'
I don't know? Cold Soldier? Bad Switch? Bad Switch logic if it's logic or relay driven switches?
Point is, this is not voodoo or rocket science. It all works the same way. Same principles, same parts (mostly not proprietary) and a volts a volt.

Granted, some techs are better than others. I, personally, was only OK at semiconductor equipments electronics but very good at mechanics and troubleshooting / reasoning. A good tech is certainly worth knowing and cultivating. It's a gift.

Tim,
I think the main thing is to shop techs. The OP was not served by the original guy who saw $$. In all my years of fixing stuff and as a process technician in a place making integrated circuits and discreet, the #1 thing I learned was to get a good description of the problem and what happened.
Asking the right questions are critical.
People don't realize they are setting themselves up with stuff like 'It's broken'. The more info a tech has, usually the better.

Is the NAD still available for inspection? I'd sure like to see it and try some contact cleaner. Worst case is you're no worse off than you are right now......

When I brought my old Carver Cube (M400t) to the tech, I was able to give a pretty good description of what / when / where and the POWER GLITCH that took it out. The electric company bought that fix for me, since I kept good records and knew exactly when my amp went south. What a Chinese puzzle box it is. It worked another 5 or 6 years after the fix, so I guess I got my $$$'s worth.

I've never worked hi-fi but this amp doesn't sound too broken for a little experiment. You may get lucky and fix it. Contact cleaner, anyone?

My preamp for the Cube was a Kenwood integrated amp that I cracked the case on, and found (sheer luck) that the main board and preamp board were strung together with jumpers. snip snip / solder and I had a preamp which lasted until I could afford a real preamp.

Rosy picture? Sure! My pleasure! No harm in trying something rather than getting a 400$+ bill for a repair. Always ask for the parts back, too. Sometimes my rants make me laugh, too.

Some audiophiles do an annual cleaning. Others will pull / clean connections and use contact stuff on 'em. I try to keep my gear is a dust resistant area, while still keeping warm running stuff cool.

Smoking and pets are deal breakers, for sure. Cats are the worlds only source for real cat hair.

Are the switches mechanical or electro/logic? I guess I gotta look up a picture of this amp!

My 1 bit of NAD ownership was troublefree for 2 decades. The piece? An old 1700 tuner/preamp.
It worked without complaint, even the remote, until the day I gave it to charity.
Prospective buyers wanted it for the phono section which I broke by doing a quick disconnect (ZAPP!)
But that was not NAD's fault. Mine entirely.

Did NAD's quality take a hit when they went Chinese? / Asian? Where were they constructed in the 70's / 80's / 90's???