Clutch slip

Having replaced the head gasket (blown in two places) and all upper gaskets to cure various leaks, and oil change to boot the engine is running sweetly. Unfortunately oil is now leaking from flywheel drain hole and clutch slipping really badly. Presumably the crankcase rear oil seal has gone and will need to be replaced. So is it better to take the engine out to get at the seal or could we go the other way and remove the gearbox etc and approach it that way? Any thoughts on the best way or how to to do it would be appreciated.

if its 3brg crank remove engine 5 brg remove gearbox

Went gearbox out route, struggled to remove 35-year-old bolts etc but eventually all out, clutch, flywheel cleaned up and overhauled, slave cylinder replaced. Rear crank seal replaced and now all back together and on the road again

Replaced clutch plate last weekend, floor out again and all, runs sweetly again with no slipage

Clutch is slipping again after a mile or two of driving, having replaced clutch plate and no sign of oil leaking in bellhousing, somewhat perplexed at what might be causing it. Are there any other adjustments I should be making?

sometimes master cylinder is adjusted too far and fluid doesnt return properly ratchetting clutch on causing slip.ive seen very few wet clutches from oil leaks, you can get poor new clutches genuine or pattern

Replaced clutch assembly, master cylinder and slave cylinder. The newish (6 months old) slave cylinder was found to be jammed solid, a bit more bleeding and away we go, hopefully