Taking the 8000T apart requires several small sizes of "torx" drivers and the habit of periodically touching the metal chassis to ground out any static electricity on your body (unplug it - the plug is not grounded). Wear only pure cotton garments and do not shuffle your feet. Act as if it were a computer - it does contain CMOS devices.
I have disassembled mine only so far, as many fasteners seem hidden by every other mechanical part in the tuner. I need the instructions (or just a hint) to remove the white bulb reflector and Liquid Crystal Display panel. Watch yourself around the LCD, it is static electricity sensitive and only TAG McLaren can provide a replacement.
The bulbs are configuration T size 1-3/4, driven by a 6 Volt direct current supply. I have no idea what wattage they are, I cannot untrap the white reflector to read the identification on the bases. If I knew the wattage, I would assemble a super-bright light-emitting diode and a current-limiting resistor to replace each bulb. They would last virtually forever, whereas the bulbs will one day burn out again.
But to R&R bulbs, desolder the two U-shaped bare wires from the main printed circuit card to the middle of the bulb printed circuit card. Clean the holes of old solder with one of the solder suckers sold at electronics stores or heat the hole and insert and extract a fresh piece of braided wire while it is kept hot. Same with removing the old bulbs.
Clean the new bulb leads by gingerly scraping the oxidization from them, stick the leads through the holes and bend them over underneath to hold the bulb in place. Next, wipe the HOT tip of your pencil-type soldering iron across a wet rolled-up paper towel, then immediately melt a dab of electronic solder onto it (the best is 63% tin 34% lead 3% silver, but you can use Radio Shack 60%-40%-0%). Immediately stick the soldered bit of the iron tip into a hole with its wire, poke a bit of solder into the junction of hole, wire and iron tip, but on the side opposite the iron tip, just until the solder melts. The melted solder will flow toward the iron tip along the wire and hole plating. IMMEDIATELY retract the iron and do not mechanically disturb the joint for about 4 seconds. If you are particular, then quickly scrub away the brown solder flux with a small disposable brush dipped in dry isopropyl alcohol. Then cut away the excess wire lead.
What you are looking for is a shiny, conCAVE solder connection (no blobs). I know they made blobs at the factory, but it is poor practice, and wastes solder. If the joint is rough or dull, you jiggled the hot joint or never got it quite hot enough (retract the iron a split-second slower). Perversely, this also happens if you persist in heating the joint for several seconds after the solder melts.
Repeat for each lead, and screw it back together.
Maybe you should practice soldering on something else first. I did when LTV trained me to solder. Best of luck.