Give it a go and see how you like it. It's a huge change though. I've just gone from dark reddy brown (about the same colour as you), to dark ash blonde. I had to do it in 4 stages. First I had a half head of foils, then gradually more foils were added, so that my hair wouldn't be ruined. And I'm only just starting to get used to seeing myself with light hair. It's been 5 months now, and I still think I look funny with blonde hair, although everyone tells me it suits me.