If you're asking this, you should probably take it to a gunsmith. This is not because it's so difficult to swap out the parts but because the new part may or may not fit like the old one did. This could produce an unsafe condition. Try to find a smith who knows the 1911 design.
If you want to have a go at it anyway, a good first step would be to get hold of some literature on how to work on these pistols. There's a bunch of it out there and most is instructive. That should save you some headaches and probably some money. Plus you won't have to, uh, expand your vocabulary.
Hope this helps.