OK, I have it working with rc3. Here is what I did:

In my theme.rc rile, I entered
*NetLoadModule rainlendar-0.20 load rainlendar.dll

When I recycled, I had Litestep automatically download that version. Then I went to my modules directory and opened the rainlendar-0.20 folder that was just created. Replace rainlendar.dll with the rainlendar.dll from the rc3 zip file. Then copy the Plugins folder from the rc3 zip file to your rainlendar-0.20 folder. You can delete the old plugins in that raindendar-0.20 directory so you are left with the updated rainlendar.dll file and the plugins folder with the rc3 plugins inside. (To do this you may have to close rainlendar/litestep in order to replace/delete files). Restart litestep or recycle and your done.

The weird problem I am having is that if I rename that rainlendar-0.20 folder to rainlendar-0.22-rc3, and updated my themes.rc file to "*NetLoadModule rainlendar-0.22-rc3 load rainlendar.dll", when I recycle I get the NetLoadModule Required Modules box, asking me to download rainlendar-0.22-rc3, even though it is already in my modules directory. Any ideas on this?

Thanks,
-Joe