you are too obsessed with blink 182 but will you be extremly awesome and tel me what u use to make these mods?
For an example:
How to get the graphics on to the garage: First you have to download Img tool 2.0 (can be found at http://www.gtagarage.com/mods/show.php?id=63)
and open gta3.img with it (is in your sa/models folder), then search for the file called contachou1_lae2.txd, then export it to your desktop, then download the program called "TXD Workshop" (can be found at http://www.gtatools.com/).
Then open the contachou1_lae2.txd file with txd editor, and find the file that looks like the front door on the garage, then look for the button that says "export" press it and press "export bmp" then export it to the desktop. now just open the bmp file with "paint" and start editing. NOTE: when you make a new texture, it shuold NOT be bigger than the original".
after that you just reverse the process. press the import button in TXD Workshop and then import the bmp file that you just edited. then close and save.
then open imgtool again and look after contachou1_lae2.txd, then delete it, then press "Add" and add your modded contachou1_lae2.txd, and close img tool. Hope that helped. P.S you can do this thing with any txd file in gta.