Does it have a mini-jack input for audio? Or XLR? Or nothing?
Can you manually control the audio levels or not?
Hopefully, you have minijack input for audio, in which case you can use an external mic terminated to mini, if you don't, you are screwed.
Hopefully you have manual control of the audio levels, if you do, then turn off AGC (auto gain control) and use manual levels (and turn DOWN the levels so you aren't clipping), if you don't you are screwed.
Next, you'll need a mic terminated to mini AND a battery box. The camera will only supply plug-in power to the mic, which won't cut it for loud shows -- you'll brick wall for sure. So, the cheapest thing to fix your problem is to get a BBox and some mics terminated to mini. You'll still be stuck with the SUCKY preamp and a/d in your camera, but at least you won't be distorting. Beyond this, things get complicated and expensive real quick. LOL!