All, I just found enough time to test out an install of the DC GV Contribution for RC1 and RC2, but onto MS2-060817. It installed very well, and so I can now say that if you FOLLOW INSTRUCTIONS closely, you should be able to get your MS2 up and running with DC GV within less than half an hour.
If you have a very modified version of osCommerce, it might take you much longer!
I can offer an installation service if anyone is interested. The charge for this will be $50 – if I cannot install it and get it working as per the instructions, you will get a FULL REFUND, no questions asked. If you are interested, please send me an email, my email address is up there ^
I also can now offer this service for RC1, RC2 and RC2a, whether or not you have contributions installed.