Advice for reviving a '87 SN 2001 after 10yrs

Good day everyone, brand new member here from central Indiana needing some advice from the experts. This season I've worked out a deal to use my cousin's '87 SN 2001. In consideration for taking care of the general maintenance, repair and upkeep of the boat, if the boat fits my needs, I'll to buy it from him in the fall. If I don't buy it, I just incur the expense to get it in usable shape for him to sell outright. So I'm pretty excited over this prospect, the SN 2001's have always been a favorite of mine, they are exceptionally flexible watercraft that can easily go from tubing to skiing to wake boarding.

So here's what little I do know mechanically about the boat:
It has been stored (covered) in his attached garage for 10+yrs
The boat was properly winterized by a CC dealer before storage
The boat was maliciously maintained before storage
It has a PCM 351
It probably needs a new water pump (don't know if that means internal or impeller)
It probably need the stuffing box re-adjusted or re-packed
It is on the original CC trailer


What I'd like to know is, what are the specific very first steps (beyond visual) that I should take to diagnose the condition of the engine and transmission once I get it here to my garage? Another cousin told me he had a 70's Mustang in a similar state once. He knew the condition of this boat before being stored and he believes that, like his Mustang, the 2001 would probably need little more than a new battery, some cleaning up and new fluids before starting. Can that be right?

I'm fairly mechanically inclined, but in-boards are new to me and any advise that I can get, no matter how basic, would be extremely appreciated.

Thanks!