With 394,000 miles and as far as I know the tank has never been drained, who knows what is in there.

I put the starter back in today and the engine spins pretty good now. I ordered new glow plugs and will reassemble when they get here, drain the tank and purge all the lines, replace the primary and secondary filters and put in fresh diesel. Is there anything else anyone can think of I should do before I fire it up?