Oil leak/burning......

My Def 200TDi is blowing oil up dipstick and through rocker cover filler cap. It is also smoking ++ from exhaust. I realised this on its way to getting it put on a galv chassis- priorities now a bit mixed up. Lost 5L on way up (250 miles), mostly from dipstick tube- chassis leg underneath soaked. Thankfully i was kind of aware and topping up as i went
I am not with the car for a few weeks but wanted to know if blocked breather causes same signs as knackered rings as I understand these are the most likely culprits. I have just replaced breather-air filter tube. Where would breather typically block?

I am going to try and supervise a remedy from afar prior to collecting vehicle and while engine is practically out of the car. Chassis fella doesn't really do much engine work:doh:
Car still running great, no noises, no loss of power and cruising at 70-75. Wasn't really thinking head gasket because of this?
Compression test diagnostic?

I have had a quote for 1500 Euro if complete rebuild needed- rebore etc. Seems like a lot given engine is already out?

Thanks

can you get cheap disco 200tdis over there ,around me they fetch £200 for a good one ,then swap flywheel housing, front housings including one bolted to block ,injection pump ,turbo and manifolds, ,

James martin's got a point there , just on the of chance coul'd it be oil pressure relif valve stuck ,put a geauge on the oil presure switch hole se what iy reads