i have a 98 f150 with a 4.6 lt w engine. how hard would it be to change out the driverside head gasket without removing the engine. have no idea about anything with OVHC.

 

It can be done but putting it back together is not fun. Handling the rear of the head and putting the rear head bolt in is the problem. Lot easier pulling the engine cause unbolting the exhaust bolts without breaking one is the trick.
Special tools are required to put the chains back on - do your homework before starting