A result of overcharging (presuming you mean excessive voltage) is your battery will quickly take on the characteristics of a hot brick of pointlessness. If it's been boiled dry or otherwise cooked, what's left of your regulator will quickly be destroyed too and you'll end up with an electrical system that only functions when the engine is running... and only for a short time before the lamps blow due to lack of voltage regulation, and possibly ending with a melted alternator!
Sorry to paint such a picture of disaster, but it's all recoverable.
Replace your battery and regulator/rectifier, preferably taking the opportunity to rewire your alternator to three-phase and using a more modern reg/rec design. If you originally had AC lighting, you should of course address that at the same time, converting to DC, to give you an easier platform on which to mount the additional electrical loads.
With a little luck your existing alternator is still OK. Continuing to run the way you describe though will probably destroy it quite quickly and you'll be needing to buy one of those too...
There are other approaches you could take, but this is probably the easiest.
Good luck!
Cheers... Paul