a) Litestep probably speeds up your computer compared to the explorer shell. It all depends on the amount of modules (can't remember the litestep term) you have loaded. The amount of dll's you load in your .rc files.
b) I don't think it'd automatically set Explorer. I think it depends on the way you uninstall. You could uninstall by removing the Litestep dir.. that'd be a bad way to do it. Through the Add/Remove Programs.. it will probably set your shell back to normal.
If it didn't still no need to reinstall. Somehow you should be able to use regedit on the registry to change the shell value back to explorer. Not exactly sure HOW you'd get to that point, so probably best you don't try it
