If I may chime in, the swank in contrib/ probably does not work with current SLIME, and mine (the ecraven one) won't work with that old a MIT/GNU Scheme. If you update to a current version of MIT/GNU Scheme, the swank on github should work fine (it's what I use myself).
You can just write to me directly, I'll try to help as much as I can ;)
Greetings, Peter