Usually the only way to upgrade from 32-bit to 64-bit is to reinstall the whole distribution.
If you don't have a lot invested in files and setting in that install, reinstalling might not be a significant problem.
But if the expert needed to go to extra effort to get the wireless network adapter working, that would make reinstalling harder than usual. Can you find out what he did?
If you decide to reinstall, unless you are terribly short of disk space, I suggest you use the partition manager on a bootable CD (such as most Debian install CDs) to shrink the existing 32-bit install of Debian to make room for a separate 64 bit install. Set up the 64-bit install as if you intended to permanently dual boot the two installs. After you verify that the 64-bit install duplicates everything you use of the 32-bit install, you can again use a bootable CD to delete the 32-bit install and expand partition(s) of the 64-bit install.
While verifying the new install you might want to switch between the two to compare any unexpected or undesired behavior of 64-bit Debian to the corresponding behavior of 32-bit. Probably 32-bit had the same behavior and you just hadn't noticed yet, but if it didn't that indicates something you should be able to correct in the 64-bit install.
Before starting, you might also want to read a few of the many other threads at LQ where I and others have discussed the merits (or lack thereof) of switching from 32 to 64. Hopefully we won't end up duplicating that discussion yet again here. Hopefully we can focus here of how to
rather than whether to
Whether to switch was most recently discussed at