I am assuming that they still have the swing keel. It is attached to the boat by a single bolt through the top of the keel and the trunk in the boat. As I am sure you know there is also an attachment for the control cable farther down the keel. The only difficulty in putting the keel back in will be lifting the hull off the trailer. As I recall, you will need to lift the boat at least a foot to get the keel back in. The easiest thing would be to lift the boat and pull the trailed out from under it. I would then put the keel on a dolly, roll it under the boat and jack it up until you could get the bolt in and attach the lifting cable. Once that was done you could crank the keel up and put the boat back on the trailer. As I recall the keel weighs about 500 lbs and the boat without the keel is about 700 lbs. So you should be able to get away with a 2 ton jack to do the job.

Before I put the keel back on the boat I would clean off any rust, paint it with ospho and then wihh epoxy and finally bottom paint.

Putting the keel back on isn't all that hard, but you will certainly want an assistant when it comes to moving that 500 lb hunk of iron around.