Not sure if there is a specific place that you need to take the motor to for a rebuild. My experience with such things with my previous cars is that you get what you pay for.
Going to placs like Canadian tire are a hit of miss! (if heard both good and bad stories with them)
Depending on where you are located, you can try this shop:
7 Harlech Court.
HOURS OF OPERATION:
Monday to Friday 9am - 8pm
Saturday 10am-6pm (sales/support)
Ask for Dave, Tell him Paolo sent you. He'll be able to asnwer any questions you have regarding what is needed to be done with the rebuilt as well as pricing.
You can rebuild it for twice the price of buying a 50-100,000km motor from japan, I would check out a JDM imported first before even touching the motor. But you can find B20 blocks assembled for 200-400 bucks. Heads are not worth much $100 maybe.