I have just started playing Simutrans. I really enjoy it. Is there a way to edit the PAK files so I can customize the details and such?
Welcome to the forum!
PAK creation is a one way process, so unless you can get the PNG and DAT files from some other source (ie from the forum or from the author), there is no simple way to reverse the process. More on the subject here: http://forum.simutrans.com/index.php?topic=270.0