For installing models (cars, peds, etc) to need to extract the .DFF & .TXD form GTA3.IMG w/ an IMG Tool, there are several
to choose from. If you edit HANDLING.CFG in DATA, keep the cars in the original order (glad I backed up that one). One
thing to keep in mind is that you have to use the same type of vehicle (not car for a bike, plane for a boat, etc) & taxis
for a vehicle designed as a taxi. Same w/ emergency vehicles.
The most important thing is to remember to back up every file you plan to edit before you start, so if it goes wrong, you
can quickly & easily fix it.