I have a 2002 Ford Focus 2.0i Ghia automatic with around 30,000 miles
on the clock.

Recently I noticed that there is a small jerk when going from first to
second gear. I checked the fluid level and it was overfilled (must have
always been) but only by around 1/2 litre. I removed the 1/2 litre and
it has improved some but there is still a 1/2 second pause after I
press the accelerator then the car gives a small jerk when going from
first to second.

I have not noticed this before, is it normal?

It is fine if I accelerate quickly but I am concerned that this could
be the start of a small problem with my tranny. The fluid looks okay,
it is a little bit darker than I would have expected but it does not
smell burned.

Wanting to be kind to my car I am planning on using Royal Purple in it
because of the reports I have heard. I know Ford now recommend 5W/20
for all Ford Focuses so the motor oil seems fairly straightforwards. I
see that the tranny requires Mercon V fluid, does anybody know whether
Royal Purple ATF would be up to the job and if so, what type should I
use? Whilst I am asking, what is the best coolant I should use in the
radiator?

Also, the tranny is a 4F27E ... I would like to change the fluid but do
not see a drain plug, am I blind or something? I assume it is not
necessary to remove the pan and that changing it 2 or 3 times will
flush out most of the old fluid. If somebody can explain how it should
be done that would be great.