Most of your running gear is probably just fine. The wiring and lights may need to be replaced but here is what I would do if you are serious about rehabing the trailer.

Remove wood
Sand blast frame
Weld in 1.5 angle sections to act as cable loom from the tonge to just in from of the first axle.
Weld on some 3/8-16 bolts to inside frame members in three locations to act as grounding positions.
Prime with red oxide primer
Paint with color of your choice
Get standard wiring scheme for your tow vehicle
Purchase 6 conductor cable to run from brake axle, usually rear axle on tandem, to coupler plus two feet.
Purchase additional wiring, connectors and lighting.
Install electrics before installing new deck wood.
Inspect electric brakes to ensure functional.
Install electric break-away system (Required by Federal Law and most states). About $45 for a good one with a built in battery charger.
Source No 1 or No 2 treated lumber for your deck.
Ensure your tires are trailer rated tires (ST series). There is a place in Sikeston, MO near you which sells complete tire/wheel assemblies at a very good price.

I have some pictures in my picture trail album showing the refab of my trailer which was basically completed earlier this year. Follow the link in my signature to find it.

Good luck.