Well with a quick search in the area looks like your best local bet is firesideliving in Laconia, their website indicates they carry most of the major brands too which is nice if you want to do side by side comparison shopping.
http://www.firesidelivingnh.com/hearth.php
Never done business with them, maybe somebody has. At least going there you can start to see what is on the market these days and compare features prices and options. All the places I talked to when I was buying my stove had a service department which included installation, however if you're not already setup to take an insert you may have to talk to somebody that is prepared and licensed to outfit you with the proper liner/vent. Also you may have to pull a permit and have the FD come inspect the job to ensure it's good to go. Code can vary from town to town. You'll no doubt have to help with the logistics of getting people and material out to the island.
Finally... don't forget once you figure out what you want to look online for any kind of deals or rebates. There is also still a 2011 tax credit good for 10% of the purchase price up to $300 bucks you can take advantage of IF the insert qualifies. For example I know Harman offers a $100 dollar off coupon online if you sign up for one and provides a list of their products that qualify for the tax rebate here:
http://www.harmanstoves.com/taxcredi...edit-stove.asp