Replacing my IP delivery valve o rings due to leakage, prompting following questions:

1. Do I also need to change the copper crush washers?
2. On this ‘87 300 SDL do I need to first remove the intake manifold (IM) in order to remove the torx screws and multi tooth hold down nuts on the delivery valves?
3. Anybody have the torque settings and tightening sequence for replacing the intake manifold and also the delivery valves?
4. Assume it’s smart to go back in with the viton o rings rather than the rubber, if so, where to buy the viton?
5. Appears this good time to replace the glow plugs ?

Will appreciate any tips on above.
thanks