Here's some pictures of a 15' Old Town Trapper that came from the factory with a fiberglass rather than canvas covering. I have done both glass and canvas and it's pretty much the same procedure.
The nails holding the ribs to the inwales are probably ring nails but they could be other style nails, you can pull the nails from the outside with a tack puller, or pry the rib tip from the inwale with a small putty knife or cut the nails with a hack saw blade.
You will have to renail all the ribs to the new inwales with 2 ring nails each rib tip, I start at the center of the canoe. You will also have to steam the new bend in the inwales at the shearline if it has a big curve at the ends before trying to nail.
Don't worry about the canoe falling apart or loosing it's shape without the inwales, if it has most of the plank still in place, it will hold together fine and will not loose it's shape. If you leave the canoe overnight you can wrap a rope around it at the center for piece of mind.
The book "This Old Canoe" by Mike Elliott covers the procedure with excellent detail. The book is really an great source of information for a wood canvas canoe restoration and the money you save making your own canvas filler with his formula and instructions will pay for the book itself.
Here's those pics of new inwales on the OT Trapper, it really makes the canoe look so much better.
new rib tips being glued before new inwales are installed,
clamping in new inwale, these inwales didn't need to be steamed first,
Openning up the area around the stem can help,
new inwales make it look really nice imo,
new inwales and gunnels, no decks yet.