I didn't see PK zip among the downloads, but the 16 bit version of Winzip should be able to accomplish the same thing. It's "nagware" but if you're going to run an old OS you'll have to put up with some inconvienence.
http://www.oldversion.com/program.php?n=winzip
If Win 3.1 doesn't support Version 1.0 of AIM I would suspect that AIM isn't a viable option.