It's a pain in the ass. I'll tell you that right now.
If you have the Mach system, remove the tweeter. Pry off the cover, then there's one screw holding it in. Use a nutdriver or phillips.
Pop out the handle thing and disconnect the wiring from the window and power door locks. Remove the screws (i think there's 2 or 3) holding the interior panel on. Slide up and off.
I took off the sound dampener paper - makes life a LOT easier.
This is the fun part. You reach in the hole - the actuator is directly below the lock button (the thing that moves up and down I dunno what to call it.) If i'm remembering correctly you have to remove a few hex nuts on the end holding the locking mechanism in place and it will come out somewhat.
Now you just gotta twist your arm in ways you never thought possible without breaking it, and work at it. The old one will pop right off, you will need a flat headed screwdriver to pry it off. After plenty of cursing and yelling, you can get it off then just pop the new one right on.
Now go get some bandages for all the cuts and scrapes you got, and put it back together. That easy!
FYI... I went about a month and a half with my interior door panel off because I got so pissed every time I tried to replace it, I gave up. It took me forever, but it's a lot better than paying the mechanic $200 to do it.