Lightening Kit + Dye Questions

Hey all, I've just recently dyed my light brown hair ----> black, and I love it. It lasted about a month until it was no longer BLACK BLACK (which I like), so I just re-dyed it black today. While I was also at the store I saw a bunch of neat color dyes (pink, blue, green, etc...) called Manic Panic. I asked the person behind the counter if the dark blue one would show up over my black hair (my hair is short and spikey with gell). She told me I would have to get a lightening kit (which manic panic also makes, lol). So I bought my dark blue dye and the flashlightning kit and went home. (I just want dark blue tips). Well just now I was talking with a friend and they kept saying I should goto a salon to get it all done, meanwhile I am already out like 30$ for all the dyes I bought to do this, lol. She told me that the lengths I would have to leave the bleah/peroxide stuff in for would basically make my hair fall out (i have thin hair, and since its black now the box says I would proboly have to leave it in for like an hour or so). So I was basically wondering if I would be safe to just use the lightening kit on my tips and dye it blue with the Manic Panic, or IS there a big risk and I should goto a salon? Thanx for ur help.