Please be as specific as possible when letting us know what is missing or incorrect. For example, say "this game's trophy difficulty should be 8/10", with a link to a website corroborating this difficulty estimate (if possible), not "this game's trophy difficulty is wrong".
After purchase and return to garage the game will offer you to automatically create new vehicle. You can also do this later - open blueprints menu, pick the vehicle and press 'Load'. For some parts you can only have one set of them on the account. When purchasing multiple packs with same parts they do not stack!
Coins - is an in-game currency, which is used to buy vehicle parts from other users in the market and to pay the rent for the workbench to produce new parts. Note! If you purchase several packs, coins included in them stack!