Greetings & welcome. I highly recommend reading and searching this thread
http://www.bikeforums.net/showthread...glish-3-speeds while you are putting your three speed together, tons of knowledge to be found there.
Three speed chains don't wear out very much and unless it is rustier than the picture appears, I would clean it with a brass bristle brush using a penetrating oil such as PB Blaster and leave it soak overnight. Hang it to drip dry for a day, soak it in any motor oil overnight and hang it to drip dry followed by a rag wipe. Should get you down the road for some time to come.
Your Robin hood appears to have been in storage a fair while, so don't neglect to lube the hub, crank, and headset bearings because the lube is probably long turned back into crude. Also oil or replace the inner cables. The brake shoes may also need replacement.
It sounds like a bit of work and money but the old three speeds can be put into very serviceable condition on a low budget (read that college) and it can be a very enjoyable process.