Do it the easy way and don't worry about wall papers and stuff.
1. Change into shared car, save game and exit.
2. Delete GAME data, it takes 5 or so minutes
3. Load GT5, download and install update 1/20 (608MB) Cancel when you see 2/20 start to download. At this point the game is at 1.05
4. Reload GT5, skip updates
5. Don't go past main screen. Don't go into GTMENU (far left option), but instead all you need to do is go to the SAVE option...second from the right side, beside the DLC option. At no point do you have to ever go into GTLIFE/Garage and change cars. Don't try to do that.
6. Select to Save, then exit, start up GT5 again and install all updates.
7. Done
Always have a backup of your game save!
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