Jeep Repair: Thermostat, radiator shop, radiator core

Question
I have a 1991 Jeep cherokee that tends to run hot
going over the mountains(in Colorado). Going downhill and running on the highway it runs at normal temps. Do you think I have a thermostat sticking and if so is it difficult to replace by myself?

Answer
You probably have a cooling system that needs a good cleaning especially the radiator core.  I would suggest having someone that knows cooling systems flush it out with heavy duty cleaners or take the radiator to a radiator shop and have them clean it out.