So, besides the game crashing to desktop half the time before it even begins the Training mission, the training mission itself can not be completed beyond the first task of switching on the rear lights. The instructor says, "Don't forget to close the door." The game tells you to "left click on the door" but without a cursor, it's impossible to do so. The cursor is only available when I'm in the cab driver view (when using Shift, of course). In other words, it is not possible to close the door from the outside.
The same appears to be true of the inner door inside the cabin. There is text suggesting you can open/close the door, but again, as I have no cursor, I can't actually do it.
EDIT: I was able to get around the problem by assigning the "Interact" function to something other than Shift, and using that key instead of the instruction to left-click.