AFAIK, yes, the only answer is to document any template/EXTRA.less modifications you made, export the style to keep any customizations you have done, make sure to save any images you use in your customizations and then start over from scratch.
Honestly.. personally it wouldn't make a difference to me what user ID they had... in fact, in some ways it could be MUCH better as you could have your actual user account at a different number than 1 or 2, locking user 1 down as much as possible.. so it reduce the threat vector of someone trying to brute force user 1 or 2, which are normally set as the super admins.