Well, I'm pretty new to this whole Reporting Services &
VB.Net/Visual Studio thing so my answers aren't as authoritative as I'd like... But they're working in my situation... I think the RDL can contain SQL, but none of the RDLs I've edited have contained any. They all point to stored procedures, which are queries, and the RDL just tells the machine how to format the output.
There are 10 types of people in the world. Those that understand binary, and those that don't.