Cool
They're great little cars that only need a bit more power to be huge fun. I'm (just - standing down shortly) Motorsport Coordinator for the MX5 Owners Club and am still a fan. Mine has a built engine and, when the BIG supercharger is refitted, will have more than enough power to be really fun!
Damp in the boot is usually the rain rail deteriorating. This is a plastic channel that runs around the base of the hood and channels the rainwater that runs down the back of the hood to the drain holes. It might be the drain holes blocked, but this more often results in water in the cabin.
First thing is to clear the drain holes. These at the side of the "parcel shelf", just behind the seat belt pillars. Lift the carpet and probe the cavity with something like a plastic rod to make sure the drain holes are clear. They exit just above the rear wheels. To get to the rain rail you need to lift the carpet and unfasten the bottom edge of the hood. It's a plastic channel that tends to perish and split, letting water run down the "parcel shelf" underneath the carpet. It then runs in to the boot via holes, dripping on to the spare or the carpet on the other side of the boot. Replacement is the best option, although repairing any splits with duct tape has proved pretty effective for me!
Your mates is defo 1994/5 vintage. The door handles/pockets are early years and the brace behind the seats was a 1994 addition. 1.6 and 1.8 gave similar power (i.e. weak!) but 1.8 had more torque and tuning potential. My paintwork is as bad as that, but careful polishing should improve it a lot. Haven't bothered with mine, that's not what I have it for.
Improvements , in order of priority
Decent tyres
Polybush the suspension
Good coilovers (P5 or Gaz)
LSD (if not already fitted)
Supercharger or turbo (road or track respectively)
Or, if you really want kit to drool over, Flyin' Miata
Result - brilliant roadster that's a bit more civilised than a Caterham but will give you a huge grin from ear to ear