My chevy trailblazer wont shift from park to drive.

SOURCE: 2003 chevy trailblazer does not move

Does it sound like it is in neutral when you have it in gear? If so, your linkeage from shifter to transmission needs to be adjusted. If you follow the cable, you should see an adjustment for it.
Turn to right to tighten it and left to loosen it.

If it tries to move but doesn't, it may be e-brake stuck. Most likely linkeage needs adjustment or vacuum line came of tranny.

SOURCE: 2004 Chevy Trailblazer Gear Shifter Moves But Will

The end of the shift cable has broken, there is a plastic ring at the transmission end of the cable that breaks. You will need to have it towed to the mechanic.

SOURCE: 2002 chevrolet trailblazer (daughter's car)

make sure the key is on and you are stepping on the brake pedal.

SOURCE: replace low beam headlight on 2003 chevy trailblazer

I just replaced the low-beam bulb on my 2003 Chevy Trailblazer. The grill just needs to be loosed slightly. Then, raise two L shaped brackets, one on each side. For the inside one, I needed to use a flathead screwdriver to get to it. The light assembly can then be pulled out. Remove the rubber cover and rotate the bulb one quarter turn left to release it. Pull out the bulb, replace with a new one ($11.50) from Advance Auto Parts, and reverse the process. Once I figured it out, took about 10 minutes total.

SOURCE: 2003 Chevy Trailblazer LT gear shift won't move out of park

The park shift lock needs adjustment. The solenoid that locks irt inplace maybe the cause of this