I just put Ubuntu on my MacbookPro4,1, but I can't find or connect to any wireless networks. I've tried installing drivers from System -> Administration -> Hardware Drivers, as well as manually patching (per this site).
All my hardware is standard, what came with the machine.
If you want to delete Ubuntu 64bit, just start from the live CD and open GParted from system-administration. Of-cause you should backup your home folder.
It is possible that your wireless card is only supported in 32bit.