I would not put a limo front with standard rear. You would get lots of understeer and the rear would "lift", not staying flat like it should. Just install the rear bar, it's not nearly as hard as you think. Plan on several hours. You'll need to support the car at the two rear jack points and have a separate jack to put under the diff, to lower & raise the subframe. I have two floor jacks & a bottle jack, but you can do it (carefully) with solid jack stands as well plus one other jack. Here's the installation instructions with some edits by me (I've done this three times now) :
http://www.meimann.com/docs/mercedes/Rear_sway_bar_install.pdf
BTW, I have a Limo front with Sportline rear, and plan to install the 500E rear soon to balance the car out!
HTH,