Catherine...if you are tempted to make your dodger replacement, Sailrite has a heavy sewing machine called the Sailrite LS. The straight stiche only machine sells for $649, the LS-Z that also does zigzag sells for $849, the sunbrella, 60" wide for about $17 a yard, the clear window plastic for???? and a DVD on how to make a dodger.
One consideration about a regular home sewing machine is the weight of the thread, and the size of the needle. Regular sewing machines generally don't handle V-69 or higher, the heavy thread that is used to sew sunbrella. Regular home sewing thread probably won't last the season.
As Peter said, using the old one for a pattern isn't always that great. Sailrite recommends putting double-sided tape on the aluminum frame, then draping plastic sheeting over the frame. The tape holds the sheeting, and you use a felt tiped pen to mark the cutting lines, or any other things you have to sew around. Remove the plastic from the frame an add a seam allowance.
If you think you might make other canvas pieces, naugahyde cushion covers, etc., the Sailrite sewing machine is the way to go--they've got everything you need--machine, fabric, thread, fasteners, thread. I have a Sailrite LS-Z and think it is great.
If this is a one time project, and you don't want make every scrap of canvas on your boat, buy a dodger.
Best of luck,
Sheila