That's a big project you're talking about there. How much are you willing to pay for it?
Well--I think until someone got in there and looked around at what exactly needed to be done, they probably wouldn't know how much work it would take. However, you're exactly right that it's going to be a big project. Indeed--that's the point! Would probably have to work out some per hour basis and some type of retainer for the right person. If we like the what you do, could probably even lead to more work on the site, as there are several different projects (besides the one listed above) for which I am in need of a developer.
PM me if you're interested and we can discuss much more specific details about payments. However--I will certainly be compensating the dev well for their time. Plus, I can pay in BTC or USD.