Hey i was looking through the russian forums and they kindly translated the instructions to get the geopard truck permenatly for me.... Here it is
I prepared the instruction too, but comrade Миха has slightly outstripped me.
1. Don’t follow Koch. 2. After Dakota’s abuse, you will appear near your Oxnard office. 3. Very slowly move to the office. Your speed must not be more than 1 (one) mile/h. A little bit faster – you’ll crash! Some says, that it’s better to use reverse, but in my practice it may be forward. 4. When the icon “to enter the office” will appear, save the game and exit to the main menu. 5. Load this save again and enter the office. You’ll see in the organizer, that Geopard is yours. 6. Leave the office and use your new truck.
P.S. I used "911"-button and this sequence too at the same time.