There are a few issues with "Service vehicle" dialog I found:

• To open the dialog you need to hold Space button. Since when opening the dialog the focus is set on combo control, and a player continues to hold the button, the control opens and closes while the button is held. I would set focus on the other control using ctrlSetFocus when creating the dialog to avoid that behavior.
• Width of control to display vehicle name is too small, as a result the name is cut off. I would make it's width at least equal to Confirmation button.

• For some reason you can't repair pickups from Reaction Forces CDLC and refuel all the vehicles (on the screenshot above I'm in damaged pickup with incomplete fuel tank, but both Repair and Refuel buttons are disabled).