Brake switch. If it croaks, the truck won't come out of Park.
While I do carry a brake switch, the knowledge of how to bypass it is far superior I think.
Here's how I've done it:
On the cargo door glass there are two wires attached. One is for the third brake light, the other is for the rear defroster. Jump these two together with a paperclip or piece of wire. Start truck, press Rear Defroster button, shift out of park. Remember to turn the defroster button off. Sounds crazy but it works.
-Tensioner Pulley. Replace this bearing for under $10. These fail and can have catastrophic results.
-Replace your belt and hoses. Keep the old ones as spares.
-Brass radiator plug
-White Coolant Reservoir, the black ones like to crack at the seam.
-Bushings. Yours are what, 16 years old?
-Tie Rod Ends
-Engine mounts, get the Jaguar V12 mounts. Part #JLM1010
-Fluids, TC and both diffs
-Wheel bearings, repack/replace.
Spares:
-belt
-fuel pump
-TRE's
-Wheel bearings
-check the linked thread for more.