1. GPUGrid's science projects only run on NVidia, at one point they started mining bit coins to help fund the research, I'm not sure they are even doing that nay more.
2. The BOINC client version you have now is fine.
3. Go to http://www.gpugrid.net/
3.1 Create your account
3.2 if you are running 660Ti or higher go to your GPU Grid preferences and select ACEMD Long runs and unselect the others
3.3 Join XtremeSystems team

4. No need to re-install BOINC
4.1 Open BOINC Manager and from the Tools menu select Add project or account manager
4.2 Select add project, select GPUGrid and follow the wizard

5. I don't think you will need to update your app_config file at all
6. BOINC will divide you GPU time between WCG and GPUGrid based on the "resource share" you set for each project (in project preferences)
7. GPUGrid is way more demanding on your GPU than HCC so I would suggest turning down your OC until you start to get a feel for temps and faults.

- I'll be brining some cards back here when WCG HCC finishes (only so much electricity in the house)

good luck and enjoy crunching
Snow