Note: This procedure requires editing a game file; creating a backup copy of the file before proceeding is recommended. With a text editor, edit one of the vehicle configuration file named "*.cfg" in the "\Infogrames Interactive\Deadly Dozen\GameData\Vehicles" folder. Look for "body_armor", and set it to 9900.0 (this may create some smoke effects, but it is not a problem). Look for "troop_protection" value and set it to "300.00" (default is 90.0). Begin the game, use that vehicle, and drive around, Let enemy soldiers shoot at you. That driver's health will increase when getting hit, over 100. If it gets to over 500 or more, some enemies will not be able to detect you, even if you get close. You can also drive around and crash into enemies.
When you find a German fortification with Medipacks scattered on the ground or on tables, get that Medipack, use it (it will be the last pack in your inventory), and look towards the exact position of the Medipack you just used. You will not see another Medipack, but if you use your "Pick Up" command (Right Mouse Button is default), you will pick up another Medipack. You can do this indefinitely, as long as you used the previous pack. You can heal your entire squad using one Medipack. Also, you can drop Medipacks, pick them up, and use this same strategy.