You're gonna love the ski, me and a lot of other guys on this forum thing that the X4 hull with the 787 is the best balanced ski that SeaDoo ever made.
I can't imagine spending 400.00 on a drive shaft, unless you take it to a dealer for repairs, if you do the work yourself it shouldn't cost over $150.00, so if that's all that's wrong it's a pretty good deal.
Of course the best test is to take the ski for a ride, I know that this is not practical this time of year in BC. Just check the ski over, shake the motor, check compression, to me if the overall condition is clean is a good indication of how well the ski has been taken care of. If the ski has been serviced by a dealer get the records.
I'm assuming the price includes a trailer.
Lou