I'm guessing that once you have passed a written test and it's signed in your log book by the CFI, I don't think you'd have to do it again, especially after only 18months.
Of course you will be playing catch up, big time, as far as your practical training goes. Expect to be doing a few more hours to get to solo and the completion of your certificate, as it is competency based, as you know.
BTW, your flight school is required to keep your training records, so talk to them.
I changed schools at about 10 hours. I had to learn a new plane, a new airfield and a new instructor, so it took time for things to settle in for me. I feel it made me a better pilot.