I owned a 90 for years. If you keep up the maintenance, you should be OK. I never really brought too many spares on even longer vacations out west.
You really don't need to bring sensors, GEMS or not. It'll limp home fine. With the proper maintenance it really isn't an issue. There is one autobox part for the park solenoid on 97 that will disable the truck, but yours is a 94, so you shouldn't worry about it.
Check your driveshaft U Joints. My truck had HD OEM springs and ate rear UJs till I upgraded to a more stout unit.
Redo your swivels with new grease, change the oils in the gearbox and transfer case and motor.
Check your coolant expansion tank. They go rather quickly but the new replacement is decent. Check all your hoses. it gets real hot under the hood and cheap hoses go quickly.
I'd throw a new rotor, cap, and plugs on it. You could keep the old ones as a spares. You can also get a nice trick unit from MSD for the engine.
Watch your heads. They tend to go around 125k miles. Take it to a local shop and you shoul dbe fine with the new gaskets and headbolts.
I'd worry more about breaking an axle than breaking down if it was well cared for.
Eric