WEG's d6 Star Wars RPG had excellent and relatively easy to use rules for all of that. Alas, d20 Star Wars, and Saga, is much more cumbersome and less clear. Saga's KISS methodology really leaves a huge frigging lot to be desired in this area. Even worse than what Saga did to hyperspace travel as compared to the workable system in RCR.
I'm in the process of converting the WEG sensors system into something compatible with Saga, but it'll be a while before I get it finished.
I'll try to answer your questions within the Saga RAW ...
SotG page 19 lists what you can do with sensors. By RAW you cannot tell what a ship has, no matter how high you roll. (Which I think is awfully stupid, BTW.)
They check your cargo for illegal items and that all your "papers" are in order. What else they check for is entirely up to the GM, as is the penalty for infractions. Whether you get a fine, imprisonment, something else, or whether a bribe is expected or useful is all up to the GM.
Beyond smugglers' compartments (SotG) and hidden holds (SaV), there isn't anything in Saga for hiding equipment. But since Saga lacks rules or allows for detecting what's inside a ship at range it really is moot. If someone boards your ship with scanners you're toast. You cannot hide from that. (Recall that in ANH Han and company ambushed the scanning team before they began their detailed search. If they hadn't Han and company would have been detected and captured.)
Well, not quite true. You can try to hide stuff. It's your Stealth (conceal) versus the searcher's Perception. If they have tech stuff helping in the search, good luck on hiding.
"My personal advice to you and everyone else who plays Saga: No matter what an official ruling is, if it strikes you as stupid, just ignore it and go with your gut."
- Gary M. Sarli