OK, I don't know if that's a problem or not. I think that it'll work, because the versions are pretty close (2.96 vs. 2.91.66), but perhaps not.
Which gcc 2.96 is this? And now that I ask, I'll have to figure out how to figure that out... probably rpm -qa | grep gcc will tell you. Certain revisions of gcc 2.96 were extremely buggy (they would not compile the kernel correctly, nor would they work with mplayer, or a lot of other programs); I believe the first 2.96 that worked acceptably well was 2.96-76 or so (it was -7X for some digit X, which I believe was 6).
If you have something older, then try to find an upgrade. I believe that gcc did compile itself correctly, though, so you might be able to do that. Maybe. If you do, you'll have to recompile the kernel, too, though, so it's probably not worth it.
If your gcc is OK, you can attempt to do an export IGNORE_CC_MISMATCH=1, then run the installer from the same shell. No guarantees on whether it'll work or not, but it might. It's easier than compiling a kernel for the first time.