Welcome to the forum and hope you find the right bike for you!
This is a great thread to keep an eye on:
https://www.buellxb.com/forum/showth...849#post609849
The first year XB's (2003) used a specific belt and pulleys that was upgraded to a wider one, then from '04-'07 they were mostly untouched. In 2008 there were many upgrades done to the engine (Thunderstorm) and Fuel Injection system (DDFI-3).
Buell XB's are rock solid, low maintenance bikes, no matter the year. Yes, it will vibrate and rattle. If you are used to I-4 Honda bikes only this will be an eye opener for you
If you like to work on your own stuff I would highly recommend getting a wireless Bluetooth dongle that plugs into the diagnostic port, and getting the program ECMDroid as an invaluable tool to diagnose the bike if theres any issues. The dongle I like can be found at Buelltooth.com, and the ECMDroid program is free(!) in GooglePlay store.
Changing the color is easy. The airbox cover is interchangable with all XB's (Uly, Lightning, even the 1125's!). The tail plastics, seats, and seat cover is the same as the 1125's, but the front headlight piece is Firebolt only.
I get my OE parts from SPHDonline, or LunaticFringe on here, don't forget Buell/ EBR is still in business and has parts. eBay is a great source for used stuff.