Just to follow on from other suggestions, the run-out (or bentness) of the shaft would have to be pretty big (in engineering terms) to be visible by eye. The op doesn't say if the prop has been off to check. Possibly damage could be limited to the prop and seals. For an outboard engineer the sort of work involved is everyday bread and butter stuff.
The ready availability of expensive second hand parts is worrying. "What shall we do with the bottom half of this motor? I know..."
As others say, Second Opinion needed!
PS apologies for no introduction, I don't even run a rib! I do have a Boston Whaler Outrage and see lots of ribs when we pass through Salcombe. Probably doesn't count though. Not quite the same thing! Oh, one of those Goldfish passed us the other day like we were going backwards.