Thank you all for the help and sorry for late reply. Ended up getting replacement boards (main and expansion) at a very good price and thankfully nothing blew up when I reconnected. I had all connections labeled with orientation, and double checked, but was still weary when flicking the power switch on!
Really kicking myself for working on it late at night, in low light levels, leading to the 1 pin misalignment mishap. Constantly live and learn!