I have not built one yet, but I'm very interested and I've just started one. Probably a one year project at the rate I can work on it.
Here's the results of some research-
Tom Moen built this one a couple years ago (as his first boatbuilding project if I remember correctly) and I just built another set of these sails for Dennis Rioux, who is building a MacGregor as we speak. I'll send you their e-mail addresses and you might want to contact them. They're both nice guys and should be able to give you some idea of what the project is like. There is a thread about Tom's boat here: http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=6758&highlight=MacGregor
Thanks Todd for the additional info- In case the questioner doesn't know it, I should have put your essential book on the list,too.
"Canoe Rig" by Todd Bradshaw