The Coffeetime E61 servicing information was invaluable to me. Thanks very much.
I just rebuilt my E61 group head following these instructions . Here are some observations pertaining to other comments:
1. I did not remove the E61 from the machine and had no trouble disassembling it. However replacing the bottom part requires a lot of upward force on the spring before the part can be screwed in.
2. Regarding the chrome flakes: the chrome plated brass(or copper?) part inside the top of the brew head on my machine(Quick Mill) was corroded with chrome flaking off, so I cleaned it up with a steel wire brush. This a good time to just flush the whole thing out since the top and bottom are both off.
3. A 7mm box end wrench(spanner for UK people) works great for holding the triangular shafts.
4. To reduce the possibility of breaking the little brass plungers when unscrewing them to change the seals, try dipping the parts in a cup of boiling water for about 30 seconds before trying to unscrew.