I have a bit of a problem, mainly biting off more than I can chew.
Well, at least you realize you've dropped yourself in it. That's a start. You should also be aware that learning ObjC/Cocoa alone won't make you a competent application developer if you aren't already, so if you don't already have a good understanding of general software design principles, abstraction, and all that other stuff, you'd best start acquiring those too. Bear in mind that unless you're a natural/genius, becoming a competent programmer is not something you do overnight. (e.g. I'm self-taught myself, and it took me a few years of writing lots and lots of really bad code and a few disasters to get halfway decent at it.)
Other folks will point you to good ObjC/Cocoa books, but personally I'd recommend the following as essential reading material:
- A good high school-level Computing Science textbook, if you've not already done so.
- Steve McConnell's Code Complete (a terrific guide to developing software)
- The Daily WTF (a terrific guide to how not to develop software)
Also do some online research on general considerations and issues involved in doing Win-to-Mac ports. You give no indication of what the existing applications are developed in, size of existing codebase, or even what they do. If they're all cleanly written in a pre-.NET version of VB, maybe you can read the code well enough to port it; OTOH, if they're some baroque VC++/MFC construction, you probably won't last five minutes if you don't already have those skills under your belt. (And if they are VB, perhaps you should be looking at realBASIC, not ObjC, as the best porting path.)
To be honest, my impression from your post is that you most likely don't know enough about what's involved, in terms of the project requirements and/or the tools and skills needed to have a decent chance of carrying it off. If that's the case, I would suggest making your excuses before you get yourself in to the point of embarrassment, and get some decent education under your belt first (both software and business). While the offer of money now must be tempting, there will always be other programming jobs in future.