Well, I disagree about the auto vs manual as far as "fun", but they are correct on both the 3.0 and the power issue. You can't swap in a 3.0 auto on a 22re. Need to find a 4 banger with an auto. Also, the 22re really is pretty sad with an auto, unless you gear the diffs pretty low. You won't feel much power until you wrap it out, and it likes to pull at 3500-4k, which the auto's don't do very well. My 87 loved 3rd gear at 60-65. It would actually hold speed on the hills and passes of CO at that, but it was running at 4-4.2k (4.88 diffs on 33's).
I also can't remember, but I think you need the auto computer as well, but I could be wrong there, the 22re may still not have any computer control. If you want to do the swap, look at buying an entire auto trans truck, so you can pull parts as needed.
However, I'd seriously consider a different truck for all the work this is going to take.