From what i understand, you bought a new router and its the dir-655
well first... DO NOT upgrade the firmware to teh 1.32. If it is 1.21 stay at that cause the firmware 1.32 is messy and unstable-ish.
completely disconnect your old router, you wont be needing that anymore unless you want to use that as an access point (like a second wifi router in simple terms but you dont need it.)
Follow the guide. it should help
so yeah, your main router is the dir-655 now... your old router, i wouldnt use it if it is a wireless G.
When you set it up, ive read that you get better preformance if you use G and N mode ONLY.
enjoy!! ^_^
once again, DO NOT upgrade the firmware to 1.32 unless you want to have lots of headaches