Check out Kurt Wulff's site:
http://www.mcdep.com
He does valuations based on the discounted net present value of future oil production. He does some fairly detailed analysis of Suncor among other companies.
You may also wish to consider Canadian Oil Sands Trust (COSWF on the pink sheets) which is a much "purer" play on tar sands.
Canadian Natural Resources (CNQ) and Petro-Canada (PCZ)are two other companies that are big on tar sands and have more attractive cashflow and proven reserve ratios.