At the bottom of the intake manifold there is a steel pan, it expends at a different rate than the aluminum intake manifold so it destroys the gasket, very very common to go bad.

You have to remove the intake manifold to get to it, it isn't rocket science but you should be fairly mechanically inclined.

 

If you read up on it and you know what you are doing and you have all the parts it can be done in 4 or 5 hrs. I just did one on my buddys ram and with two people working it took no time at all.