If you're just looking for a different finish, the most popular thing to do with the Marlin's is just refinish the wood stock. Lots of people just use black epoxy paint with no alterations, while some people take the opportunity to slim down the forend before they paint it. Both ways look very good on the guns that I've seen.
The hardest part is getting the Mar-Shield finish that Marlin uses off the stock....it's very durable and from what I've read about the process, no one has really found anything that will readily dissolve it. They just sand the finish off while trying to not damage the wood or checkering in the process. I would think that with the ability of some paints to adhere to just about anything, just roughing up the finish on the stock would be enough for the paint to stick to it. If you send it out and use one of the "super" coatings like DuraCoat and the like, then you don't have to worry about ruining the stock (if you are worried about it).