I have an 02 4.7 that I got in January, as well as an 06 5.7L Hemi.
I absolutely love both trucks. The hemi is a Laramie, so it's almost unfair to compare it to the 4.7 ST that has almost no extras.
The 4.7, like any engine, requires regular maintenance and TLC. Something that wasn't told to the previous owner of my 4.7, evidently.
Check the oil on the 4.7 that you're looking at (and all the other fluids for that matter!). Mine was sludged up. (Regular oil changes will prevent/ slow that!)
This contains some pics, a better summary of problems I had and recommendations that I received. )
Not sure how motor inclined you are, or where you're buying from.
If it's a backyard sale, ask if you can take it to a mechanic (preferably one that you trust not to give you BS), or even something like Advance Auto where they'll hook their code reader up and see if anything shows. If they say no, I would be nervous. Very nervous.
Heck, I do the same thing when I go look at a vehicle at the dealer! Just see what they say, and if they're okay with it, do it. If they're not... JMHO, but I wouldn't be buying it. Also, if it's a dealer, ask if they offer a warranty! (The warranty on mine saved my rear end!)
I love my 4.7L-- 'Silver'-- and I'm happy with it, and will definitely be taking good care of him. Just wish the previous owner had done the same!
I'm getting 15.6-16.8 MPG on Silver (4.7) And at last check, the Hemi was getting 15.5 mpg, but that is on the lower end, I think. Both trucks are mostly highway.
Just remember that I don't go slow in my 4.7 and my MPG suffers (I need a bumper sticker that says "Drive it like you stole it"), it's more common for me to get closer to 15.6 ish mpg, though it is possible to get better!
Don't let my 'horror story' scare you away. There's tons of guys that have a 4.7L that they love. Another person on the Z to ask about the 4.7 is RogerRamJet (I'm sure that he's already welcomed you to the forum on your profile)!