CS4 Action & editing questions

Once you have created an action is there a way to edit them? Example if I wanted to add and/or remove an additional step within an action, how?

Within my actions I also create layers for each adjustment so I can tweak each photo if needed.

Also, I am finding it difficult to remove blemishes once the actions are completed...

Example:
1) Duplicate main layer
2) Run Noise Ninja - label layer
3) Run G. Blur @ 10 reduce opacity to 35% add a mask - label layer

4) Create an Levels layers adjust black point (left arrow) to output 5 - label layer

Now once the action has completed and I want to remove any blemishes which layer would I make the corection? I understand that the "lower" layers is not a good place (because they are covered by the upper layers) but if I try to make the adjustment on layer #3 (G. Blur) using the "heal" brush there is no effect. If I remove the mask, still no effect. I am using the wrong "tool" for this specific layer (G. Blur)?

Or should I be creating the blur affect after I have removed any facial blemishes?

Now if I work on the photo without running the action first, duplicate the main layer first then remove blemishes then run the action everything works as I expect. Is there another way? Possibly less time comsuming? Or does it all work out to be the same?

Please, what am I doing wrong or is it I don't really understand "layering", help...

I am just a beginner, finding out wonderful new tricks every time I take the time. I have finally started creating actions 1) because they are way, way faster 2) Now I am getting a more consistant "look" accross a batch of photos.

Thank you in advance for your time and consideration.
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JM
Climing the learning curve for CS4