I changed the cam shaft seals on my 92 400E, which I belive has the same engine as yours.
I can't recall exactly what I did, but it should not be a difficult job as long as you can remove the top cam cover on each cylinder bank, then remove the distributors and then remove the front cam cover, to remove the two intake camshaft seals you need to remove the variable valve timing acuators, two exhaust camshaft seals are easier. I can't remember how I took out the seal, but at least I am sure I didn't use any special tool.
Yes, when you put back the front cam covers, be sure to seal covers with special paste, I simply bought some oil resistant high temperature automobile silicone. It has been a year since the repair, not a single drop of oil since then.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.