This is a sum of my 2 1/2 years of 6.9 experience.
1) Spheres - unless you know the history of the car or else it is performing flawlessly they are likely to all need replacing so that you can start with a known quantity. They are in my opinion the single most important part to get right first.
Front spheres and centre sphere are 6.9 specific (Red Dot painted on sphere) , rear spheres are shared with 126 with full hydraulic suspension(Blue-green dot) and I was quoted AUD$760 each from the local M-B agent 2 years ago. They are available for considerably less in Australia as non-genuine replacements (ask Styria) or from the US for about US$150 each but expect US$200 to $300 for postage costs due to size and weight.
Tom Hanson at The Classic Centre, Irvine, California (E-mail him at
thomas.hanson@mbusa.com for a quote) will provide genuine M-B parts at quite reasonable prices with very reasonable postage costs and gives a 15% discount for members of the M100 Club.
I have used
http://www.autohausaz.com several times and have been very happy with their service particularly when you use their lesser priced postal service instead of USPS.
Spheres for rear Self Levelling suspension look the same but are a lower pressure and not suitable (?Green Dot - not sure).
2) Genuine M-B Hydraulic oil - M-B agent price $65 per litre but they sold me 5 litres for $39 per litre when I haggled. Can be found for AUD$25-29 elsewhere.
3) Struts - Rear dust boots can be purchased from M-B agent for about AUD$70 each. I hear strut ball joints go for about $400 each from M-B agents but I have purchased two rear rebuilt ones from Styria.
The struts themselves really only need replacing when they leak on the floor but
http://www.adsitco.com has rears in their catalogue for US$600 each and fronts for US$750 each. Having dealt with this guy it wasn't an altogether pleasant experience so I would get the total price including postage before you start.
Rumour has it that Tom Hanson sells genuine ones for about US$1000 each.
4)Front and rear control valves - are apparently no longer available. I have two nos 126 ones which came from Saudi Arabia via e-bay and are my "treasures".
I have seen "reconditioned " ones advertised on German e-bay for about 700 Euros but I am sure they can be easily reconditioned by anyone in the hydraulic or aerospace industry.
The rubber dust boots are not available.
5) Pumps - the original 6.9 high pressure pump is no longer available and is usually replaced with the SLS one of which there are lots about. Rumour has it that they are about $1100 new.
6) Central valve - no longer available - presumably will need rebuilding if you have problems.
7) Hoses - dealer supplied or no doubt can be rebuilt by any hydraulic hose supplier eg Enzed.
The system although relatively complex is also quite reliable once any obvious faults are fixed.
The most useful piece of advice I received from Walter who owns "The Star Shop" in Perth is to drive it - a 6.9 is not a car to leave sitting in the shed.
Bill