Sounds like you have some pins stuck to me. If the key slides in and out too easily that may mean that something is gummed up. Maybe try inserting the key and tapping it with a small hammer. Don't bang it too hard as you don't want to break the key but tapping my get some movement. Also try and tap as you rotate the key. Once you get it open I would take it off and see if you can get some graphite lube worked in there.
If you can get it open and the lock out. I am not sure how hard it is to remove, maybe try some bake cleaner to clean it up, blow it dry with a compressor or let it dry then lube with graphite. Someone may have lubed it with WD40 or some form of oil at some point.