Oil change on the 4x2 should be easy. You don't have to remove a skid plate I don't think. I don't remember seeing one on mine at least. You are fine to go ahead and get it changed. Some say sooner the better.
As far as miles per gallon. You are running quite normal for this truck. You see some people with a few mods get a little better but not much. You have to remember your truck is still not broke in either. Give it some time it may get a little better but don't look for any miracles. Remember this is a V8 not a v6 you are going to use some gas. Also it has a lot to do with your style of driving. Do you have a heavy foot at take off? if so you are going to burn more fuel than driving easy. I have a really hard time with this because I just love to punch it. LOL
Oh well thats life I guess.
M4ck
As far as miles per gallon. You are running quite normal for this truck. You see some people with a few mods get a little better but not much. You have to remember your truck is still not broke in either. Give it some time it may get a little better but don't look for any miracles. Remember this is a V8 not a v6 you are going to use some gas. Also it has a lot to do with your style of driving. Do you have a heavy foot at take off? if so you are going to burn more fuel than driving easy. I have a really hard time with this because I just love to punch it. LOL
Oh well thats life I guess.
M4ck