Does the new head come with the valves installed?
The labor cost is very high, sounds like about $100+ per hour. There is no mechanic in the world worth that much an hour to me. Of couse I would do it myself. Where else could I make $100+ per hour tax free? You could too.
I wouldn't replace any glow plugs unless the old ones were bad or the vacuum shut valve. There parts rarely go bad and if they do, they don't prevent the car from running or do any damage. If the cam timing is 3 degrees or more late, then a new timing chain is should be installed and maybe new chain guides..
P E H