Congratulations on your purchase. The 140s are very nice vehicles. I can't answer all of your questions, but I'll do what I can.

Here in the U.S. the best service manual for the 140s is the CD manual available through any authorized MB dealer. You might want to check with an MB dealer to see if they can get one for you.

If I remember correctly, the pump for the central locking system is located beneath the rear seat. I don't remember if it's on the driver or passenger side. Before you go taking out the seat you'll want to check all the fuses first. Keep in mind that there are two fuse boxes. One is under the hood on the driver's side right in front of the firewall and the second one is in the trunk on the right hand side directly above the battery. There are lists in each box which will allow you to locate the correct fuses to check.

40 psi in the tires is quite high. The recommended pressure for my 140 is 28 psi all around for a normal load and 28 psi front/34 psi rear for a heavy load. Good luck. I'm sure that once you get these minor issues resolved you will be very happy with your new 140.