Fast Purchase

Have a short question: I found a car after weeks of searching, which we find very good. The dealer has already made me an offer by e-mail, including the payment of my old. On the weekend we drive to my parents – because there is the new car nearby – to test. Here is the real question: I assume relatively sure that we will also take the car. How long does the purchase process take so generally? There is no chance that you can do this directly on the You can do the weekend like this (including the car change and take the new one), right? Are you going to drive more than 300 km, and if we decide next weekend: Yes, it will be annoying to go back a weekend later to pick him up. What do you think?