K series camshaft seal replacement

[Graham D]

The front exhaust camshaft seal has developed a slight leak; can this be replaced without disturbing the camshaft?
Secondly, is there a problem with the Piper branded vernier pulleys? The red anodised finish on mine is wearing away and I have a vague memory of other folk having a similar problem.
And finally; are there any problems with aftermarket coolant pumps – are they as good as the originals?

Thanks in advance, Graham