Tom,
Welcome to the Forum.

Here are some links to help you out with your Santa Fe Hudson.

First link gives you some history of the 665:
http://www.postwarlionel.com/cgi-bin/postwar?ITEM=665

Second link gives you instructions for maintaining your Lionel Trains:
http://www.justtrains.com/Service/maint-main.asp

Third link gives you  repair tips for your trains:
http://www.slsprr.net/technical/PopSci%20RefLibr%20No.15.pdf

As for a transformer, just about any transformer that provides 18 - 24 VAC. peak power should work for you.
Amperage requirements will depend on whether you're pulling lighted cars with your loco and if you're trying to also power accessories with the same transformer. 

Dave