Garmin
I can also recommend Garmin for a GPS. I have had Garming for 4 years and couldn't be happier. I have a Lawrence hand held I have had for years and years, and although way outdated in technoligy, it still works fine, and serves me well as a backup. I also second the recomendations that you get a harness, and tether. When single handing, there is no outside help, so you are on your own. One thing I do when it gets really snotty, is I rig a double tether, one to each side of the cockpit, just to make sure that if I should go over, I don't get into the water. It is virtually impossible to get yourself back on board a moving boat, if you are being drug along by the boat. The double tether does limit movement, and is only usable when at the wheel, but it does make sure I can't get completely over the side.