My wife and I did ours on Welch nine years ago, about 11 square. Quite a bit of work but also quite doable. Some friends to help would be great as long as they are reasonably handy and comfortable working on a roof.
There is a lot of good info on-line about how to lay out and install shingles. You really need to plan it out first if you don't have prior experience. It was three boat trips to get the new shingles out there. We borrowed two roofing shovels to remove the old shingles.
http://lawn-and-garden.hardwarestore...el-614132.aspx
As disposal of the old shingles from the island was an issue, a friend suggested that we carefully remove the old from top down trying to keep the old shingles mostly intact. We bundled them on the roof using lots of duck tape (many large rolls) and dropped the bundles down for stacking and later transport.
We did one side at a time and had large blue tarps along with strapping to nail down and cover in case of rain.