Cheap and quality FR dont go together. Is it easy not really, can you put it in yourself if you have the tools and know what your doing, yes. If you dont have the tools or dont know what your doing its a good way to ruin a guitar. But there is no cheap way of doing a quality job.
What's the guitar? It's an afternoon project to mount one on a Strat. It's a major operation to put one on just about anything else. Also, Tackleberry nailed it about cheap and quality with FR's don't go together. The cheapest is probably going to be a Gotoh, which run about $100 IIRC