Based on Xanathar's, the potion of Invisibility could be sold for 20,000 gp
Selling magic items also takes a week at least of downtime. I am all for selling it, that’s good money and we have multiple people that can already cast invisibility. However adding up all the other downtime activities we would be spending a couple months just hanging about. I say we take one week, two at most.
Nikola has three basic goals he wants accomplished. He wants to sell the rod of the pact keeper +2, and possibly the potion of Invisibility. (All proceeds go to the party) He wants to do some research on the dungeon, maybe find a map or two that are accurate. And finally he wants to craft a Gem of Seeing with the vial of moon water. With help, he could craft it in 5 weeks or double that alone.
Let’s hold on to the rod of the pact keeper. I have a feeling we will have a warlock at some point.