After calling the local specialist it seems it’s probably the head gasket gone. He can’t fit me in till at least January

To be honest I’m not sure if I have the time and motivation to get it done so thinking of selling as is…any thoughts?
It’s a really tidy 1984 Autosleeper Trident 1.9DG which I’ve owned and looked after for over 10 years. Excellent condition inside and very original….bit of seem rash on the outside but nothing serious.
MOTD till end of March, currently on Carat wheels with decent van rated tyres, big bumpers, newish leisure battery etc.
Maybe I’ll regret it but in two minds about what to do, and not sure what it would be worth as is?