So we're gunna expedite the RP part of this a bit. If you're going to try and gather information, you can choose to do one of the following:

Talk to the Criers. These are guys usually set up outside of bars, clubs, and gambling halls trying to advertise their businesses. Most of them are fairly professional and generally won't go out of their way to direct you to other competitors, but a sufficiently strong or sweet word (Intimidation or Persuasion) can get some information out of them.

Talk to the homeless. These are vagrants and orphans who generally migrate around the city either doing odd jobs or petty thefts. They go a lot of places so there's a good chance you might find the right one who might've seen Sandwich or the Drow Gang. Naturally of course they don't give this information for free. They want at least 20 GP for any information, though they could be persuaded to lower the price unless you can offer a better deal (Persuasion).

Finally you can simply start looking on your own. Unfortunately, Gilgan already disposed of the drow corpse so not really a way to use the body itself. However you do still have the chip, and Eastern Paladros is relatively smaller than the other sections. You'd simply roll a Perception or Investigation check and we'll see what leads you can find.

If there's any other means or methods you wanna try, just ask em here.