Congrats on the new toy!
Ok, I can walk you thru disassembly/inspection/reassembly on the 102C when you get it home, I do it regularly. First, buy some Comet Clutch lube($13) so you will be ready. They will not last but a few years if left to the elements without lube. You will also need a 102C puller($20) to do the job.
The silencer... I personally would avoid the DG silencer unless you want to go deaf! LOL On one machine, I run a DG pipe but swapped out the silencer for an $5.00 Ebay TRX250R FMF. I had to modify it to fit and fab up some mounts, but works fine(much quiter too) EEE makes a good silencer too.
Plugs... Book calls for NGK BR9ES, or BR8ES(cold weather). I have run even the BR7s(hotter) before with no problems. I would highly suggest avoiding Champion plugs at all costs. I have chased many a problem that was caused by Champion plugs.
For climbing power and harder excelleration(torque, go with a 22" rear tire, high stall setup in the 102C and a smaller carb(32mm-35mm). For more top end speed, go with a 35mm-39mm carb and 24" tires. Ofcourse, they make reeds and exhaust pipes that are setup to help make power in the different areas too. Best HP gains will be made thru port work and polishing which can be a rev or torque port job.
When you get it in, post up and we'll help you get it dialed in for what you want. We can also figure out what has been done to it already.
Gary