Home highlighting for long dark hair

Hi everyone! I am brand-spanking new to this site as of yesterday and am just thrilled to have found you all. I spent all day yesterday and half of the night reading about colorfix and fillers and highlights. Wow - I didn't know there was so much I didn't know! Of course, though, I am here because I have some questions I hope you all can help me with.

My hair is about mid-back length, very good to excellent condition, medium texture with a lot of hair. It is a natural dark brown but even when I was younger it would always lighten up as it grew.  I have been coloring my hair various shades of brown and adding the odd highlight for at least the last ten years. Not on a regular schedule  - just some limited highlighting in the summer then usually back to a darker and more uniform brown once fall or winter would roll around. The last two years or so though the few gray hairs have sprung up more frequently and although I really don't have many (maybe 1 percent??) they are mostly on the crown and temple areas so no matter how I part my hair or wear it the white hairs really stand out on the dark brown background. This has led me to doing root touchups more frequently.

A few days ago I used Excellence creme (medium brown mixed with light ash brown) and came out dark brown as expected. It is almost the same color as Andie McDs color in this link, although mine is more neutral in tone:

http://www.lorealparisusa.com/frames.asp#http://www.lorealpa risusa.com/haircolor/products/excellence/index.asp

I had planned on doing a lot of highlighting with a cap at home to brighten it up but realize now that the cap with the long hair isn't going to work. I also have decided that I want to go back to a lighter medium brown  so I can have the beigey highlights I have always wanted. I am considering going the colorfix/filler/recolor/highlight route but am also exploring my options for a less radical approach and doing just the highlights at home to brighten things up.

And that, finally, leads to my first question: If I do the highlights, I will have to do them myself. I was going to try the Loreal Highlight Styliste in creamy caramel since it is 30 volume vs. the toasted almond which is 20 volume. I want to try to tone down the orange so I am planning on using the Loreal tone refiner after highlighting. From what I have read, lots of you don't favor the drugstore brands. So, just my luck, a Sally Beauty has opened up near me. Does Sally sell something that will work better for me to do the highlights versus the Loreal Styliste? If so, what is it and what do I ask for? Does using a protein filler have any place before highlighting? How can I tell if my hair is "average" or "above average" in porosity?

Thanks so much for any comments you care to offer!