I recently removed my duron processor from the cooler to gt it off the motherboard and I noticed it tore to thermal pad. Can I just use thermal paste/grease to replace the thermal pad or will I have to find another thermal pad?
Replacing the thermal pad with thermal grease will even result in better cooling. In order to do it properly, make sure you remove as much remnants of the old pad as possible. Lapping the heatsink surface would be the best thing to do, but if that's over the top for you, you can use 95%+ alcohol & a lintfree cloth to clean the contact surfaces as good as you can.