Hey RobMickey, I'm playing catchup reading old posts, hope you are still around. Pretty snazzy upholstery, I think I will shy away from silver as my stock SX Lightning interior successfully lights my ass on fire after some time in the sun.
The heat exchanger is likely the one for the v drive (canister looking thing on top of v drive)there's one under the starboard side exhaust manifold as well for the transmission. This was a source of a leak on my SX, it was not winterized properly There is a 7/16 drain plug you can reach from the passenger compartment (along with the block drain on that side)
Both devices can rupture from bad winterization. I believe the transmission one is a Mercruiser part, can't confirm. Both can be repaired easily locally.