I'm finally gonna get the red streak down the middle done, but i'm thinking how hard can it be, baring in mind I've never used hair dye before.
Surely its easy enough for someone to apply it just down the middle without getting any on the sides or should I just go to a professional and pay more for it?
not that i think you should, see above arguments against it. It should be quite easy to do, altho you may want a friend (one you trust) to help you out. but its not that hard to dye hair in one place as most hair dye is quite thick like gel and you just apply it where you want it.
Personally i'd pay to get it done proffesionally. It might cost about £20 but by the time it needs doing again you'll be bored with it so its only really a one time cost.