Warning: If you are not competent or do not feel comfortable doing any of these modifications or procedures, then please do not do so. I will not be held responsible for any damages caused by a result of your actions. Now on to the fun stuff!

This should work on all e36 BMW 3 series. This was replaced because the factory plastic pieces were falling apart and many of the mounting holes were cracked or simply tore out.

Materials:
1 JTD Under Panel (available from JT-Designs)

This includes all the hardware you should need so long as your inner fender splash shields are intact with good mounting holes.

Tools:
Wrenches and Sockets
Jack
Jack stands

Procedure:
1.) Chock the front wheels, jack the car up, and support it with jack stands just to get enough room to work under the front of the car

here's what you'll be looking at at this point

2.) Remove the two side plastic pieces (see picture). I can't remember what type of hardware holds these pieces on. I had rivets from a previous repair I'd made!

3.) Now remove the center plastic section. I think this has something that hooks into the back of the radiator shroud, but I may be wrong! (sorry I did this while ago!)

4.) Now you'll need to preassemble the three pieces of the JTD panel. It's really easy. the two black pieces are held together by a bent verticle piece with some machine screws. This verticle piece fits up into the bottom of the radiator if I remember correctly.
The whole deal should not be tightened down until it's in the car and mounted. It takes a little playing with to get it to fit right, but you'll know when you've got it in there. I used an punch just to aligne some of the holes. It came out pretty nicely in the end!