Oooops, one more question. :-)
If I just rebuilt the source rpm, then I guess I need to build a binary package after I install the newly rebuilt source package, right?
Nope; if you "rpmbuild --rebuild" a src.rpm package you'll just get the binary packages built on your system, no new src.rpm. It would be equivalent to "rpmbuild -bb specfile". If you do "rpmbuild -ba specfile" you'll get a new src.rpm but unless you've edited the specfile, it won't have any significant differences to the src.rpm you started with.
Cheers, Paul.