There is an uninstaller in your OP installation folder called "dipmodelremover.exe" that should restore your OP installation to stock from the LB5 shiplist installer. (a fresh install is not necessary) Also there is a folder in your OP installation called "dipmodels\backup" that has whatever shiplist and strings files were present when LB5 was installed. (If you want to temporarliy swap them manually)
As drb mentioned, most mods have a shortcut to the uninstaller on the start menu or in the control panel add/remove programs dialog. The uninstallers will restore whatever files that were present when the mod was installed. Just keep track of which mods you have installed - I generally only run one at a time, uninstall the mod, then install others.
I'm playing on LB5 when not working on my servers at the moment, all the action is there. (I'll keep an eye out for ya, I'm flying Klingon as Wkaah...
) Glad to hear you're interested in the SFB-OP server but to keep things simple you may just want to wait till LB5 is over, it will still be there and I'll still be working on it... Though swapping out mods is not that difficult once you get the hang of it.
There is also a shiplist swapper you may find handy, Strat's
SFC:OP Mod Chooser Tool, though I have not used it myself...
P.S. in order to see the D2 servers, don't forget to update your WONServerSetup.gf according to:
Attention: Please Read, this is important!, if you havent already...