Wirelessly posted
I've installed BES Express on multiple SBS2003 machines myself, all without issue. I followed the standard BES installation doc and everything worked just fine. I've even done this remotely via RDP, but I doubt that makes much of a difference. If you need any pointers during your install, please don't hesitate to PM me for my email address.
Of course, I'm also willing to offer my services for a price.