Novice needs a place to begin to restart this 326,000m 1981 300TD that supposedly ran last summer but now only turns over.

Getting some white smoke, Turns over quick enough. Glow plug relay works. Glow plugs show proper resistance. Considerable blow-by via the breather. Turbo is lunched but would this prevent a start? Doubtful, right?

Where do I begin?. Would like to get it running before contemplating a rebuild.

Thoughts?..Suggestions?...Ammunition?

Thanks..Frank