ls3swap

1998 camaro with ks3 swap. The car will.be dyno tuned once I get the 411 pcm and harness setup I have done a lot of searching but need additional clarification on this swap. Im Gonna buy one off eBay and have it flashed for a vin. I already have the have the 99 up harness mod done. I just need to know besides having it flashed for a 99 up camaro what else needs to be done?
1. Correct fuel segment or file is that done in the flash or is that additional work to be done.
2. What exactly has to be done in the 411 pcm in order for my 98 fuel gauge to work?
3. Can I give them my 98 vin or will I need a 99 up vin to have the 411 pcm flashed. If so how do I go about getting a 99 up vin to flash

Thnx