You'll need to give me a little more info, what year, what engine, what do you intend to do with the car?
Swapping a complete engine in and out will take a weekend, fixing a spun rod bearing isn't something that you will be able to do without a machine shop being involved. Swapping your top end to another built short block is possible so long as you are up to the task of phasing the cams and reinstalling the chains.