splitting the cases isnt hard, i would say even if you get the used one for300 split it and get new seals, possibly some bearings, and fiber clutch plates, and if it has a center gasket kool, but if not, i suggest using 3m rubberized sealer, i think its a hondabond 30.00 for the tube,but it is better than yamabond or suzukibond
i would let the guy know this and see if you can get the motor for less, i bet- a local shop could do it for a hours worth of work ,i know i could and they have all the tools ect... if they say anything different they are full of crap, a tear down is fast, unless they break something ect...