Do I Have the Guts?

It's sitting there in the closet. Mocking. Daring. Threatening. I bought the box earlier this week and stuck it up on the shelf in the closet. I walk by the closet door and stare in longingly. Do I dare? Have I really got the guts to try coloring my hair? At home? By myself?!?
Just buying the box was daunting. There is an entire aisle filled with hair coloring brands. I looked hopefully through the displays, trying to find the color my hair used to be. A dark-brown-but-definitely-not-black shade. None of the brands offered that. How many different shades of brown can there be? Dark brown, brown, ash brown, maple, hazelnut. And if that's not enough choices, they also throw each shade in with a "light" or "medium" offering. Medium ash brown, light maple brown.
It did not help that I had four boys with me, ages 9-14. They alternated between being bored and pulling out some really odd-looking colors obviously not found in nature.
Some of the boxes have color charts on the sides or back. The "if your hair is this color, this box will make it this color". Only some of the before and after shots looked no different from each other. One brand showed the before shot in a blurry haze and the after shot in clear, crisp tones. I get it--your product will make my hair more vibrant--but the color charts should be for helping the uninitiated. They shouldn't be part of the advertising.
I spied one box that said 100% gray coverage. That sounds good. But then I noticed they all said that. Is it possible that all of those brands are that effective? I finally took a breath and focused on my goals. I want my gray hair hidden. And I want my hair to go back to the dark brown shade it used to be--instead of the black that the coloring shampoo has made it. And I don't want a drastic change. After looking at all the shades of brown, I realized that I really want to do this a step at a time. I might have to got through several cycles of coloring over the next few months to get my hair shade back to where I want it to be. So I chose a brown a little darker than what I want, but definitely lighter than what I have.
And now we're home. And I'm plagued with doubts. What if I don't get my hair colored evenly? How do I get all the hair covered in the back? I'd hate to finish the job only to see I have a darker stripe down the back of my head where I missed a chunk of my hair. And what if it drips down my face? Will I have a dark streak on my forehead for the next 4-6 weeks? What if it doesn't do a good job of covering the gray? Or worse case scenario: what if my hair turns some weird shade of dark purple?
Okay, now I have a a new worst case scenario. On the box it says to test a small area to see if you're allergic. What if I have purple hair and huge, swollen lips? What if my husband comes home and finds me dead on the bathroom floor with strange purple hair? My obituary would read, "She died of vanity." (Come on, you knew this would end up with somebody dying, didn't you? After all, I am a suspense writer!)
Most of the guys in my house will be gone this evening, making it a perfect time to try out this project without interruption or commentary. Except I don't have that 48 hour window to see if I'm allergic to it. (I don't actually have any allergies, but that's not the point. Do I really want to find out too late that hair color is the exception to the allergy rule?)
I want to do this, but I'm just scared out of my wits. I never get things right on the first try. How public do I want to be with failure? If any of you have experience in home hair coloring, I'd like to hear it--the good and the bad. Then tune back in here Monday to see if I had the guts to take the plunge.