Litestep.exe is installed to 'C:\Litestep\....that is where your existing shell is....with subdirectories for themes, etc.
the extracted files from RC3 do NOT have a step.rc or anything to do with configuring....you have all that already.
Just copy the entire Litestep directory and subdirectory....NOT MOVE.....to a temp file....just in case....eg....c:\temp\.
Then
copy [overwrite] the RC3 files.....to c:\litestep\ and you will be prompted with 'do you want to replace'?....say yes....and it's done....