I've got some links to prior discussions on this topic below. I hope you find them useful. I'd say the posters above have given you the same advice I would have. I'll try to add something new and say chartplotters, while not needed, are easier to understand than the more basic non-plotting, waypoint only, GPS units. They cost a bit more but if ease of use is paramount my gut says spend the extra $$s (something I wouldn't have said 2 yrs ago). You can look and see your position with respect to easy to identify features (islands, bays, points, etc) vs some perhaps forgotten-what-it-means-where-is-it waypoint symbol. GPS is useful at night and in bad weather as well, just remember it's not radar nor x-ray vision. The fixed mount unit's require that you also mount a separate antenna and run a co-ax cable, as well as power and ground wires. This may or may not be easy for you. A removable unit with an internal antenna is easier to install but I'm not sure you can get one w/the more complete Bizer chart of the lake (this was mentioned in one of the posts below).
http://www.winnipesaukee.com/forums/...ead.php?t=1610 (scroll down to upthesaukee's post)
http://www.winnipesaukee.com/forums/...read.php?t=562
http://www.winnipesaukee.com/forums/...read.php?t=150
http://www.winnipesaukee.com/forums/showthread.php?t=69 (scroll down to Silver Duck's informative post)