If the "tech" is Vince Galbo of Advanced Audio, I would'nt hesitate. He performed an amazing upgrade on my Plinius M-16 preamp. He undestands Plinius equipment like no other, and keeps you in the loop throughout the process.
You have to look at what kind of kit can you get for around $750, not a whole lot that will compete with the Plinius. The capacitors have a life, in your case 15 years. That doesn't mean nothing else will ever fail but capacitors are the one item that should be replaced. My Krell is over thirty years and I replace the caps myself every 10 years rain or shine. If you like the amp and I'm guessing you do get it repaired otherwise sell it and take the gamble you'll find something you'll enjoy for the next 15 years. What did the Plinius cost? divide it by 15 for your cost of ownership then add $750, still acceptable. I believe Neil Gader from the Absolute Sound listed this amp as one of ten of the most significant amps of all time, not bad.
A real shame it died because the 8150 has some nice reviews out there, warm and musical if memory serves me right.
I would not spend $800.00 + to get it fixed however.
If you could find one used (a long shot) it would be a little over $1000.00 I bet.
Maybe you could shop around for another tech like Nick Gowan from True Sound, maybe he could help.
My two cents...
If you love the Plinius, the answer is easy. If not, it might be a good opportunity for a change. From a pure cost standpoint I would consider what you might get for it on the used market as is, add that amount to the cost of repair, and see if there is a newer integrated you could get for the total amount that you'd be happy with. For example, if you got $300 for it, a newer integrated in the ~$1100-$1200 range would make sense financially. On the used market, you can get a lot of amp for that amount.
I think it would be really hard to find something as lovely as that amp for $750. I do this: I flip a coin and if the coin says the same as my gut feeling then it validates me and if the coin says something opposite to what I felt I wanted to do it highlights my inner thoughts about the repair / upgrade whatever.
Your question is "Should I repair a Plinius 8150?" and to that I would answer a hearty "yes". To replace caps is not a big deal and replacing the switch should be basic as well. Learn to solder and get going.
Study the web to see how caps are changed, practice a little soldering, buy a new switch and have at it. This is probably one of the easiest DIY things in electronics. Just be sure to discharge the capacitors before starting the job.
I read this thread days ago and had all the same thoughts as Viridian, just didn't feel comfortable saying do it yourself without experience, But now that he has said it....
open the case, take pictures of the wiring for reference, look at and measure the physical size of the caps. Get the value of the caps... i.e. 10,000mfd 50v etc.
If you can replace these caps, any good cap with the same MFD rating or higher AND the same voltage rating or higher(larger the value the better on both) that fits will do a good job.... a 10,000mfd 50v cap runs $5 to $30 USD. As Viridian said, some parts have improved, you should come away with better performance than before the repair.