how much should you expect to pay depends on the damage if just the wear ring and the impeller is not chipped you will get away under $100 and some cussing here and there if you do it yourself, if the impeller is chipped or bent a question of how much should not be asked the impellers are not cheap most on average new go for around $300 just for the impeller. Anything marine spells money.
Its not that hard to fix, search the forum and you will find all the info you need to do the job right.