If you go to the file path GTA5 -> plugins -> LSPDFR -> LSPDFRExpanded there should a .sav file with the name of your charakter. Open the file and there you can change your xp, money and much more.
It is a very cool mod that you created. But it would be even cooler, if we could buy different aparments (or just change the interior) with working garages to store our vehicles like in online mode. If not, the mod is still one of the coolest.
And is the coming features to specific ranks like rank-specific vehicles?