If you're doing head gasket, might as well do valve seals while it's off.... I hear they're a real headache to do while the head is on......
While you're doing that, might as well put all new upgrades seals into the IP, and replace all the plastic hoses on the IP... Might as well put new seals in the turbo as well. It's a lot easier to take it off while the engine is out... (ask me how I know).
Look into timing chain and guide rods as well...

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All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic