That looks like a nice score. Nice bonus to have the rudder casting upgrade, and you're lucky the front cross bar has the reinforcement plate since the '84-'87 models' hulls are known to fail without the plate. Judging from those two it looks like the boat was well maintained and mostly needs some elbow grease, new lines, and bungee cords. Try using Bon Ami or Barkeepers Friend to clean the boat and sails instead of a power washer.
It looks like the previous owner either didn't know how to remove the traveler and main blocks from the rear cross bar or didn't bother. I like to store my traveler, blocks, and sheets in the cat box.
Lube the traveler track, mast luff track, and main sail luff with a good silicone spray or McLube.
If you have the pop off hatch covers they are known to leak through the rope handle and it is recommended to switch them with the screw covers. Just drill out the rivets and pop in some new ones sealed with silicone, and you'll need a pop rivet tool to do it, so get a good one with two long handles instead of the small ones at the local hardware store.
Another source of leaks is the rudder gudgeons and hull plug housings. If a hull takes on more than a cup of water after a day of sailing then try removing and re-sealing them first because they are the easiest to do. I used Life-Calk.
Check the tension on the bolts holding the hulls to the cross bars. You'll need a big Allen wrench for the inside ones.
Consider replacing the tramp lacing, and whether or not you do then get the lacing as tight as you can. Low stretch line is advised.
Learn how to drill out and replace rivets. It's not difficult and it tightens the boat as well as seals it from leaks.
If you have the money, time, aptitude, and desire then I encourage an upgrade to Hobie 20 Tiller Connectors.
Old rudder cam tension screws over many years of neglect can become one with the lower rudder casting, and if this is the case with your boat then search the forum for how to remove them. Jeremy at Surf City Racing has an instructional YouTube video for that: http://www.youtube.com/watch?v=zUUA7l6fzIk
Check the rudder cams for wear or slop, and replacing them is easy. Rudders should lock down and unlock smoothly. If you need to drill out the rivet holding them in place then be very careful not to drill into and widen the rudder casting hole.
That's all I can think of for now.