well, if you DO put in an alarm/imobilizer, I'd suggest two things: 1. Don't set up the damn thing so it automatically sets when you get out of the truck on the trail, and 2. If you lockout the ignition, take the key with you so some dude doesn't drive your truck when you're helping someone else get out of a hole at the bottom of the hill...
1. Do a search on here... tons of ideas re tires, size, lift, etc
2. I don't think you can do locks if you have a ST, but I recall some post a while back for SW.
3. No idea
4. Mount the GPS (presume it's one of Garmins) to the dash next to the ashtray. They sell a dash mount with adhesive tape that works just fine.
...ok, only one REAL answer