Pamela, I use a waist level 90% of the time on my 645, though I do have a prism finder - no winder. The question I would ask myself, if I were in your shoes, compared to the cost of said finder and winder, could I get another lens or how much film,paper,developer could I buy. The winder and prism will not make your images any better, they could make it easier to take, but balance it with what you need now. Don't forget, there is still a large supply of equipment out there so pace yourself.

Just my 2 cents...