I notice when I drive for about 30min or longer, my temp gauge rises to almost "H" then it goes back down to the middle at normal temp. It never stays on "H" it's like a floating Gas needle. What could be the problem?

 

you may need to change your thermostat. not a big deal. doesn't sound like it's opening enough or it's opening too slowly.

my friend had an identical problem with his durango the other day and considering a new t-stat is only around $10 i figured it would be worth doing first. worked like a charm.

 

Is that something that I can change myself or I need to take that to a mechanic?

 

If you can change the brake pads, then you can do it. If not, then you shouldn't do it.

 

Its actually not hard to do. You have to know what you are looking for in order to do it but Im sure you and a friend would be able to figure it out. Just follow the bottom coolant hose and you'll see what Im taking about. Its two 10mm bolts. First drain the coolant and than undo the 10mm bolts take it out and replace and refill and your good to go.