Welcome to Trainz.
As I understand your question, you want to put a tunnel on a built-in track? If so, then yes, you can do this by inserting spline points either side of where you wish to have your tunnel and deleting the track between them.
There are a few options available for tunnels, some have scripting which means you only have to connect the track to the tunnel entrance at either end and little else. Others require you to use a tunnel spline to connect the two tunnel portals and then the dig hole tool to remove the ground from the entrance when you raise the level around the tunnel. It sounds confusing but is simple enough.
As for wipers, not all locos have this as an enabled function. Others have automatic wipers and some you can turn on and off yourself.