A 1/2" drive breaker bar with the correct 1/2" impact socket for the lug nuts (I don't recall the exact measurement - someone chime in if they know off the top of their head) and you are good to go. You can find them at your local Autozone, Pepboys, etc. Shouldn't run you more than $20 for the breaker bar + socket, then you just have to purchase the replacement lugs. Screw out, screw in. 15 minute job for all 4 wheels.
Something like this:
http://www.autozone.com/autozone/acc...er=391361_0_0_
and this:
http://www.harborfreight.com/13-piec...set-67903.html
You don't have to buy the set, just buy the correct size if you want ($4-5 for quality ones)
Oh and while you are at it, a torque wrench is a good thing to have.
http://www.harborfreight.com/1-2-hal...rench-239.html
Helps tightening the lug nuts to correct spec, something BMW service NEVER does for me, I'll have you. Always overtorqued.