First off, you should visit the Apache section. One of us probably knows the boat and can tell you if it's ever been dunked or broken. Second, you need to have the boat professionally surveyed. Unless you don't mind a $10,000-plus surprise, you need a pro to do a thorough checkout. If you're financing it, you'll most likely be asked for it anyway. If you've yet to get insurance, it will most likely be a requirement.
Is the owner doing the re-commissioning or are you? 4 years of sitting is a stretch and not knowing exactly how it was laid up brings everything into question. It would need all fluids and filters as well as a thorough look-thru. The fuel in the tank is probably bad. I'd also be concerned about a motor that's had the valves sitting open in one spot for 4 years, not to mention the toll it takes on valve springs. You can do a startup but they'd have to be immediately replaced before running if it were me. A leakdown test on the motors is a must.
Nothing wrong with TRS drives- there are still parts available as well as used drives.