You need to replace the O-rings and copper sealing washers. Yes, you need a splined socket to get the delivery valve holders off. You CAN do this job without removing the intake manifold, but it does make it very tight.

Tightening sequence for the DV holders is 30NM, release, 30NM, release, 30NM, then final torque to 35NM. That's torque and release to 30NM 3 times, then final torque to 35NM.

If you do the tightening too loose or fail to torque and release, expect loud injector nailing or difficulty starting when the car has sat. Been there, done that.

If you're ordering parts, do the springs as well. They will have to come from a dealer, or one of the dealers who sells parts online. They're not expensive and you will notice the difference in length and stiffness.

Critical: Make sure everything is SPOTLESS (as in you could perform delicate surgery) in the area you're working. Any dirt that accidentally gets in the system can cause you problems later!

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]