Engine & thermostat heating up

Thank you, was afraid it may be water pump, I have had to replace it twice before and I have also replaced radiator. I am now ready to replace Jeep!

Thermostats are a cheap part ($5-8), if you take it in somewhere it'll be mostly labor fees. It's also a total DIY project if you're handy at all.

Just curious, where is the thermostat located? Is this a part that a non mechanic like myself can replace?

4.0L? http://www.wjjeeps.com/service/cooling.htm - scroll down a ways. It bolts in place with basic tools, but you will have to drain some coolant and deal with the thermostat housing gasket. If you've never done it may want to leave it to a pro. Otherwise watch some youtube vids on replacing a thermostat for your make/model, or pick up a repair manual. Autozone's website also has free online repair guides.