Replacing 3.0L with a 3.4L on a pickup

I've got a 92 extended cab pickup with a 3.0 engine that apparently has gone bad. By that I mean. A few weeks ago the engine began to knock from the right side of the engine. The noise would start when the truck was started up. About 15 to 30 seconds later it would dissipate and almost dissapear. You could still hear it but not as bad as when the engine starts. The truck ran fine, The other day I started it up and the noise was back, but all of a sudden there was some other weird noise and the engine started to sputter and there was hardly any power. No smoke, the engine has oil, etc. I think a rod went out or something. Anyway, I don't want to try and repair the engine as I don't have time, but I've come across someone who is selling a 3.4L engine. My question is: Can I replace the 3.0 with the 3.4 & what changes would I need to make if any? Thanks, George