Installing TB shouldn't be any real problem, but to remove OE is some kind of a pain, and I just left mine rather then doing it. I wish there was a program that would do it for you.
In winXP that does not work. You can also uncheck IE but we all know it doesn't remove it either. It will remove the shortcuts but the program is still on your PC. In fact you can delete the folder outlook express and it will reappear with outlook express still there or it won't let you delete it at all.