Find the program : "3docoll" to help with your collisions.
1: open a .3do with it.
2: for now just do 1 collision volume.
3: save .3do as differnt name.
4: open up the .3do in GPL Editor.
5: add new string called "collision" (without quotes)
6: goto node DNAH "HAND"
7: double click on the next node in the tree.
8: enter value of newly added string ("collision") in
9: goto MIRP "PRIM" -> collision tree root, keep going till u
get to an empty node
10: right click on empty node, insert -> replace with flavor 4
11: insert the value of child nodes, how ever many sides to
the wall (minimum = 3)
12: replace the new empty nodes with flavor 6
13: replace the next new empty nodes with flavor 16
14: replace next empty nodes with flavor 10
15: double click on the new flavor 10 nodes and insert a value
between 1-20 (1 being really hard, 20 being really thin/soft)
16: with the flavor 6's you added earlier, double click on
each one of those and add the plane number in which you want
the collisions to be around.
19: run around in a circle (joke)
20: test in GPL, by ramming the object as hard as possible
Hope this helps somewhat, just to get you started.
Here is some more really great collision info by Guru.
It is particularly useful to get a grip on planes as you will need
to create a "convex hull". The convex hull is just a fancy name
for the surfaces you want to crash into. (As long as you don't
want to crash into some kinda of crazy doughnut!) If you
accidentally make a concave hull like I did the first time you
will crash into it and it will crush you and send your car
bouncing off the top of the horizon. Tip : don't make a collision
shaped like a cave
After you understand how to pick out the three points of a plane
on the evil geniuses page you will be ready to pick out the
collision planes from the many planes that make up your
object. Pick out the plane points in 3doEdit using wire frame view
and enter them into this spreadsheet. Remember - counter
You will have to enter x,y, and z coordinates for each point I, J,
and K. Then you will see the A, B, C, and D parts of the plane
definition and will be able to easily pick the plane number out of
the plane list in GPLEdit. Now you have the plane number for
step number 16 of Scott's collision instructions.