As a rule, when you buy a used boat even if the impeller is working, you change the impeller.
unless of course the owner tells you that he literally just had it done.
i did an impeller on my 130 on my front lawn having never done one in my life and I found it very straight forward. Hardest part was realizing how to twist the housing down on the rubber so that it would actually go into the housing. It’s one of those jobs that because everything is intact to begin with and typically nothing is broken, you simply disassemble and then just reassemble in the exact same order with your new parts (gaskets, the impeller) the hard part on a big motor can be re-aligning the gearshaft and that’s just because it’s heavy as hell. On a small motor, easy Peazy can be done by yourself.
youtube is your friend for sure!