I think you're going to have a hard time getting any decent amount of money or trade value for the GL1. To get an approximate value, you can check eBay. If you search Canon GL1, you can click "more refinements" on the left and tell it to only show "completed listings." Then click on "sold listings" at the top of the page. That'll tell you how much people are paying today.
Right now it looks like they're selling for anywhere between $150 and $350, depending on accessories, warranty, etc.
