This could mean:
1) Turbo oil seal has blown.
2) Piston rings have gone.
Get a mechanic to check it out, and after you check your turbo and if its alright get a Compression test on your cylinders.
Its only around $110 for a new oil seal in your turbo, so no need to replace the whole unit. If you change to a bigger turbo you will have to have the surporting systems to go with it. eg: afm, fuel pump, injectors - to be safe and ecu to get it tuned correctly.
If its your pistons rings that are shot through, Its time for a rebuild and some forgies .
hope that helps...