Mate, this is based on worse case scenario, but if it's engine out and splitting time then it's a few hundred £ even if you are doing it by yourself, a gasket set for that is about £120 from Wemoto let alone any bits you may need.

Trust me I know, mine got stuck in neutral once and it was a complete rebuild job.
I'm not saying your is though, no idea yet
I've sent you a PM