Welcome, sir! Not sure what your plan is with the truck mod wise, but there's a decent amount of things you are able to do to these trucks, surprisingly. When I first got my truck my parents frowned upon me modifying it. (It was my grandfather's and I bought it off my grandmother for $3500 98k miles). They still do but for some reason Trailblazer parts just keep showing up to my doorstep that I may or may not order myself.
If you want to do some LED upgrades, the blinkers, reverse and taillights all use 3157 bulbs which most of us pick up on eBay. The rear blinkers do require the CK LEDs. Dome lights use T10/194 LED's if you are looking to upgrade those as well
Just trying to be brief, if you want more info, feel free to take a stroll around here as there is a ton of info packed into this site. Once again, welcome to the family.
Ryan