Easy question, I hope.

Does anybody know what size the oil drain plug is on a 1996 Land Rover Discovery?  I don't have a big enough wrench or socket to fit. It is metric right?  Also, do the wheels have locking lugs? It looks like a cover over the actual lug itself. I bought it from a guy and I haven't seen or heard of a lug tool and I don't want to mess it up.
Thanks,
Donnie

The lug nuts are 27mm,, no locking lugs it sounds like that the metal covers are messed up. 
The oil plug I have always used a large adjustable wrench.

http://www.landroverforums.com/m_49881/tm.htm
 
Read this post. But it is a 1 1/16" SIX POINT socket for the lugs and 1 1/8" for the oil plug.