Pls go to the RTO office in BDA complex off Old Madras road. You will find a lot of brokers there. I normally used to use Philips Driving School, but they have gotten greedy now a days. Their work is good though.
Why do you want to re-register your car? I have used a AP regd bike and a KL regd car for over 15 years without any issues. (YOu just need to know the rules )