General :: Migrating To 64bit Quad Core System

In the past, I've deployed new 64 bit systems and I've worked on and developed on 64 bit systems. But until a week ago, my workstation was a 32 bit system. Now, it is a 64 bit quad core Phenom II system, and I suppose I need to start the migration to 64 bit Linux. I do not want to blow off my system and rebuild it. This particular system dates back a decade and through many many updates. There is some digital debris in it, but there is also a fair amount of customization that I have implemented either for my own purposes or for customers, and to lose that customization would represent a headache for me.

What I want to do is install a 64 bit system over top of the 32 bit system. It is my hope that doing this would install the necessary 64 bit libraries, while not impacting the existing 32 bit libraries (except with some possible symlink problems). I then, hopefully, could boot into a 64 bit kernel while still running 32 bit programs. Is this feasible? My backup system is comprehensive; I COULD just try it and back up if my system became hosed. But I'd rather not; I have a lot of work to do and I'd rather not learn by doing in this case.