Yes you'll have to switch to IIS if you require SSL. We have a help page for setting up SQL Monitor on IIS although I don't think we go as far as to give advice setting up SSL:
http://www.red-gate.com/supportcenter/C ... M_UsingIIS
Note that you don't need to re-install SQL Monitor. Creating a website in IIS Manager and then pointing it at the "C:\\Program Files\\Red Gate\\SQL Monitor 2\\WebSite" directory should do the trick. Also it's possible to have IIS and the XSP servers running simultaneously on the same machine as long as you use different port numbers. So you can continue to use the XSP server whilst configuring IIS.
Hope this helps