Two problems, AC and Putting in Drive

I have a 2004 Trailblazer. Which has been a good vehicle up till now at 55M miles.
First problem is I am having a hard time getting it to go into gear when pushing down the brake. I know it has a switch but I do not know where it is or what it is called.
Second is the AC. It is having a hard time staying on the cold mode when starting the car. Sometimes I have to restart the vehicle for the AC compressor to stay running. The freon is not low. I figure a relay is getting bad but as above I do not know which one is probably the culprit or where it is located.
Any help on these two problems would be appreciated.
Thanks

If you are having probs with your AC, is your fan clutch bad? It is a very common problem on TBs, so you might look into it. For the shifting out of park, sound like your brake solenoid is bad and needs to be replaced.

Do you use the hand breaks? I have problems with shifting out of park as well. However, someone here suggested that I get into the habit of using the hand breaks.

Now I park and pull the hand breaks. It helps with shifting out of park. I would shift out of park the release the hand breaks.

Since you have 05, you better have it checked out anyway.

a/c, low side pressure cycling switch may be going, been a common issue for the past few years on trucks/suv's.

the other issue may be a bad BTSI solenoid.