The screws that hold the end castings and the sheet aluminum covers together all use standard Phillips cross-slot heads unless someone changed them.
The thing to keep in mind is that the screws are mostly threaded into shallow sections of soft aluminum. The aluminum threads wont bear much force without tearing out the threads. So, when you put the screws back in, its a good idea to coat the threads with Locktite #242 REMOVEABLE Thread locker. This keeps the screws in place without over tightening and possibly damaging the threads.
To replace the bulb socket you need to remove the right end cover (as you face the front), the rear panel, and a few other parts and screws that will be obvious as you disassemble. The upper part of the rear panel is actually a light baffle open at the bottom for the cooling fan exhaust.
Replacement GX5.3 sockets for the Dichro II lamp house with the white woven insulated conductors and clip-on leads already installed are available from KHB in Mississauga, Ontario.
http://www.ebay.com/itm/Lamp-Socket...677?pt=LH_DefaultDomain_2&hash=item588c925a5d
Sometimes the existing bulb socket can be made useable by using an old bulb to clean the contacts inside the socket. By spraying the holes in the socket with tuner cleaner and inserting and removing the old bulb 10-15 times, the friction will sometimes abrade insulating corrosion or other debris from the contacts and allow the bulb to operate normally. I recommend trying this first before replacing the socket.