Stuff you will need:

TimeI did all 4 in 1 afternoon
14'x8' sheet of masonite (cut into 4 - 2'x4' sections) - $7 at Lowes
1Roll speaker box carpet - 54"x36" roll $20 crutchfield.com (you'll have a bit extra)
2Cans 3M spray glue
1Hot glue gun and assorted glue sticks for the trouble spots that don't stick
4Your old door and side cards
1Optional black trim screws
1Scroll saw
1Drill assorted & drill bit sizes
1Body file to clean up the edges if you can't cut so good
1Scissors

Steps:

1.Remove your old door cards and take all of the clips off of them.
2.Remove the covering of your old door cards or trim the stuff away from the edges as we will be tracing these guys.
3.Place a door card on a 2'x4' section of masonite and trace the outline. If you removed the covering from the old door card you can make the clip holes and other assorted holes you will need to make later.
4.Cut out on your line you draw with the scroll saw. It's better to cut outside the line then cut to much off.
5.Drill the holes for the retaining clips and cut out the other assorted holes you will need.
6.It should now look a lot like your old card. Clean up any edges with a file if you need to.
7.Place the new card on your speaker box carpet, or other material, and cut around the card about an inch.
8.Per the direction of the spray glue. Spray both the carpet and the door card with glue and let sit until tacky.
NOTE: Follow the instructions for whatever glue your using.
9.Place the two together and press firmly. Don't worry about folding any edges or cutting anything out yet. Make sure it's flat and there are no wrinkles in it and let it dry for a bit.
10.Fold the 1" extra around the edge of the door card and trim as much of it off as you can. At most you want like an 1/8" on the back side of the card. Spray it with glue and get it in place. Use hot glue as needed. Do the cut outs for the door handle and such the same way. I'd suggest cutting and X in the hole for the door handle and window crank hole and it make it easier to fold and look nicer.
11.Install clips and mount.
NOTE: Optional mounting would be to use some black trim screws. This would require that you drill hole through the door card and sheet metal to mount the panels. I used a combination of screw and clips as I ended up breaking half of my clips do to their age.