I once bought a home perm kit and used to to try and straighten my hair, it did not work at all, not very surprising really!
Make sure you also buy a really good conditioner for chemically treated hair and use it the week before you straighten it and from then onwards. A good salon will only let you have it done if your hair is in very good condition because it takes a lot out of it (unless you get the really expensive Yuko system that Jenifer Aniston uses, which is £240+ a go) so bear that in mind when you do it at home. Good luck with it, let us know how it works out.