] I was watching P&P2 the other night, and I had a couple of questions about Cheapside.

] 1. What is it? Jane said her uncle lived in Gracechurch Street. Later Caroline hisses that her uncle lives in Cheapside... she knew right where it was apparently.

Yes, she knew. Cheapside was a part of London, just behind (northeast) St. Paul's Cathedral and west The City, and precisely where many people dedicated to commerce had they warehouses, as you can conffirm in the link below

Gracechurch Street, where the Gardiners live is in Cheapside (in the outskirts if I understand correctly) just follow north the London Bridge and that is Gracechurch Street.

] 2. Did the word "cheap" have the same connotation then as it does now? Is that what made Cheapside so abhorrent to the Superior Sisters?

As answered above, people in commerce lived and worked there, I imagine it gives that connotation you remark even if one does not know what and where is Cheapside.