I'd be concerned not being able to check compression... like they said ^ starters are not bad price-wise and can be replaced without removing too much. Maybe just the airbox and a long ext. with a swivel socket.
Check the VTS, full range, they're known to go out. Check the weld plugs on the exhaust (top chamber aft. mani), if it's a saltwater boat and not flushed they could be corriding out. Might also want to pull the lid to the rear black electrical box and look for signs of water intrusion, corrision. Fuel gauges sometimes don't work b/c the float falls out, easy fix just pull the pickup assembly and fish float and/or magnet out of the tank. After that just do the usual checks like impeller cond, wear ring, etc.
Watch price.... 99 SPX's weren't a dime a dozen like the 96xp, 97-98 SPX's but I wouldn't reach vs. settling for the earlier years. Sure the 99 might be the best color scheme and the hump seat is ok, but not worth a considerable amount of $ more IMO.