Good call, CP. A large water change will not stop what little progress you may have made. Don't replace anything. Don't wash anything, just rinse. Always use conditioner/dechlorinator. The chlorine kills bacteria.
The bacteria is in the air. It's hard waiting for it to fall into your tank and start multiplying. Waiting five/six weeks is not uncommon. If you can afford it, try Tetra Safestart. Many people have had good luck with it. If you're ordering online, and can afford a few dollars more, try Dr Tim's One-and-Only.
Good luck. Keep us posted.