You CAN use it though to receive NASA-TV, and the FTA music stations on the 119 sat though. But otherwise I agree that a 36" dish would be better.
Your old dish might be OK though. My dish is REALLY in bad shape. I have dents the size of soft balls in it from knocking snow and ice off in the winter, but it still receives Ku OK. Of course you'd have to upgrade to a C/Ku feedhorn or LNBF. My theory though is that when a big dish is used for Ku, that often only the center of the dish is really being used, because the scalar rings are really only functional on
C-band (this is just opinion... probably wrong), so if your dents are out toward the edge, they might not affect Ku that much. That's the case with my big dents, ie they're near the outside bottom edge of the dish, where I banged it with a broom, and they don't seem to hurt Ku that badly.
You can experiment, and attach a ku lnbf along side of your C-band feedhorn. I've done this with a circular lnbf for the more powerful DBS sats. It works, but not very well, first, because there is only one true focal point, and secondly because it's hard to get it at exactly the right place, so it could take quite a bit of experimentation. You have to put the little lnbf on the east or west side, not to the top/bottom. On mine, I'd receive about 10 degrees west of where the main feedhorn was receiving. I eventually took this down and went to a 36" dish with a linear/circular lnbf.