I'll tell you as much as i know, and let others take it from there.
If you know what a vent is, you are getting close to the answers you are asking for. The second word is easy; it's "drain". Once you know where your building's drain is, draw it out and post it. Also, the vent in the roof is usually directly above where it is in the building, so draw that in or tell us.
How they plumbed your garage is anybody's guess until you tell use what drains are there and where they go (connect to) before going out of the building.
It's easy once you start with drains and vents in a floor layout. Then, it is possible for someone to tell you how to connect the plumbing in between, no matter how many fixtures you want all together in one space. It may be "hard" or it may be easy, to do. A toilet needs a big drain, but before you conclude that it will be "hard" wait and listen to feedback.
About the electrical panel: you can turn it 90 degrees so it now is in a new wall perpendicular to the one it now is in. This can be done without "moving it" so much that it needs new wiring.