If you intend to dive it, I would have it overhauled by a Mares shop if you have one in your area. While it hasn't been used, the rubber parts are 10 years old and may not be in great shape. That being said, the MR12 is a great regulator for the kind of diving that you are interested in doing. Mares still sells the MR12 on their Proton and Axis lines. You could upgrade to a newer regulator, but I imagine that your current regulator probably wouldn't fetch anymore than around $150 - $200. Also, for the diving you describe, I don't think that a newer regulator would necessarily make a big difference in your dives.
If it were me, I would get your reg serviced and ready to dive. Do some dives with it until you get some experience. Once you've done some diving, so can more easily figure out what features you feel are necessary to the kind of diving you do, and which are less necessary. At that point, you'll be well equipped to purchase a new regulator, and you'll still have a dependable MR12 as a backup.