Ok. Tutorial Time. Jared you might want to pin this one
BEFORE ANYTHING IS DONE: extract the moded files from their zip/rar and into a specific folder. THIS STEP IS IMPORTANT
1)You must open IMGtool, click file, open, *find gta directory*, open data folder, and select either gta3.img or player.img
2)You then must find the files you want to change. since the most common mod is cars I will use the cheetah as an example.
* a fast way to find the files to replace is to click edit, find and type in the name (cheetah)
3)Click on the file(s) you want to replace (cheetah) and click commands, extract. chose a place to put these files for they will be back ups.
4)Once backed up you can continue on to click commands , replace. * make sure that the files you backed up are still selected* then find the new files with the same name and select them.
Thats it. and If you want to save yourself the hassil you can always download SAMI.
Its Long but precice. Let me know if i missed anything