You can look at the guide that Ben, David and Don created for porting SQL from Oracle to PostgreSQL at openacs.org/doc/acspg. It's not an easy task especially when there are new versions coming out frequently.
What I think would be best for you to do is wait until ACS 4 comes out. We are waiting for ACS 4 so we can port it to PostgreSQL and it's going to be much better to port it because of the new aD database API.
Porting to MS-SQL now would be a waste of time and effort, unless you want to stay with ACS 3.2.2 (or 3.2.3) forever and lose the delicious goodies in ACS 4.
