Turbo cartridge

I get occasional clouds of blue smoke at idle then runs fine for weeks so I'm guessing turbo oils seal is wearing out
Has anyone changed the turbo cartridge ( a new turbine and bearing assembly)?
It would be much quicker for me to do this as I wouldn't have to send turbo away for a rebuild - I could have cartridge and fit it on same day

Any advice appreciated

Before you think it's turbo check the plenum none return valve on the back of the engine, if it's failed this can cause smoke.

Fitting a new turbo cartridge is very easy and a lot cheaper then having the original rebuilt, I've fitted many since they became available on Fleabay, just be careful tightening the banjo bolts as I remember someone on here saying it cracked the body.

Thanks for that
Have checked the oil breather and seems ok
Think I'll order a turbo cartridge to have on standby anyway