To replace the oil pump you need to pull the front cover and in order to do that you need to pull the harmonic balancer, radiator, etc. If you’re replacing the pickup tube because you’re replacing the o-ring then nothing else besides the pan needs to come off. I take it you’re concentrating on the o-ring and doing the pickup tube while you’re there? If so, I’d stick with that. I doubt your oil pump needs replacing. Here’s a great article that covers the oil pump among other things. Bookmark this site, it’s got great info.