"Where can I get blueprints or drawings of how my pipes are ran, doesn't somebody have to keep those?"
While we keep blue prints of the houses we plumb we don't keep a record of where the sewer pipes are run. That's because a sharp plumber can locate the house cleanout and get the measurements from the city as to where the city raiser's located and look from the clean out to the raiser and figure how he would run it and pretty much be bang on. We're not talking a complicated situation here. This is a single pipe that goes from here to there.
It doesn't take a rocket scientist to figure the shortest way to get there.
You've already stated that they ran into trouble about 40 foot out. That's a start. I would call a plumbing repair company and have them snake out the sink line and tell you what you have under the ground. Good luck, Tom