I need to replace my low beam bulbs but cant figure out how to get the old bulbs out. any help would be greatly appreciated. Thanks
Can't give you specific directions for a Trailblazer, but, generally speaking, the bulb will be in a holder that either clips into or screws onto the back of the headlamp. You may have to move some wiring or a windshield-washer reservoir or the battery to gain easy access (or find someone with small hands :-) Once the holder is out of the car, you'll either find the bulb can be removed from the holder or there will be some clips you'll have to undo before the bulb will come free. Take the replacement bulb and just reverse that you did to get the bulb out -- but don't touch the bulb. If you do smear skin oils (or even grease from a rag) on the bulb, its life will be a lot shorter (and you'll have to do this again real soon).
If you have the owner's manual for this truck, it should have instructions. It also will tell you what kind of bulb you need to replace (they're not all the same). If you don't have the manual, the parts store should have a book which will tell you which one you need.