My car is about to hit 65K miles and since I have a small leak on both valve cover gaskets, I figured I'd take care of the 70K mile service and then some.
Here is my list of items being listed to do, and where the parts were purchased from, and part numbers.
I am having this done at Audi by a qualified technician. Has worked on the car in the past and offered a great deal; will know more once all done.

- Valve cover gaskets
Part Number: 077198025A (set of 2)
Purchased from ECSTuning.com; they sell each side separately or you can buy a set; chose the genuine Audi set;

- Timing belt
Purchased the whole kit on the RS6.com group buy; preventive maintenance given I am close to 70K miles; you can buy the whole kit from blauparts.com
The RS6.com kit included the Water Pump and Thermostat; the blauparts.com kit is enhanced to include these as well;

- Cam tensioner and seals
Purchased the whole kit from blauparts.com

- O2 sensors
Part Number: 1K0998262AB (set of 4)
Purchased from ECSTuning.com; chose the genuine Audi set;

- Coolant sensor and retainer clip
Part Numbers: 059919501A (coolant sensor); 032121142 (retaining clip)
Coolant sensor and retainer clip

- N75 diverter valves
Part Number: 06A145710P (set of 2)
This is mainly for preventive maintenance, given the car is now 12 years old; purchased from ECSTuning.com

- Alternator/Voltage Regulator
Part Number: 077903015RX (alternator); 0031546506 (voltage regulator)
I have not had any issues thus far, and found on RS6.com that usually the voltage regulator is what can fail due to age;
Purchased the Voltage Regulator instead and this will be done as part of preventive maintenance;
Got the part from RMEuropean.com

- Bufkin oil cooler pipe
Purchased from James Bufkin PE Bufkin Design and Engineering (jamesbufkin@bufkinengineering.com);
Great and quick service on getting the part; preventive maintenance; no issues with the stock plastic piece, but it is known to fail;
Useful details and installation instructions;

- G40 camshaft position sensor
Part Number: 058905161B
Purchased from RMEuropean.com;
Preventive maintenance given the age of the stock part;

- Motor mounts
Part Number: Left: 4B3-199-379-J Right: 4B3-199-379-M
Purchased at the dealer; preventive maintenance given the age of these items;

- Starter assembly
Part Number: unknown at this time
Purchased at the dealer; preventive maintenance given the age of this item;

- Oil and filter service
Purchased at the dealer; required given the valve cover gasket service;

- Transmission fluid service
Purchased at blauparts.com

- Check for any oil leak on turbos


I decided to post this list because I compiled it from various previous posts. Lots of information but even so I felt a bit lost until I started to research where to purchase items, and what should be done. Made sense to post in this format for others to help themselves as well.