NOOOPE, don't do it at all. Not for cash. This is a big mistake. Bloggers like these are generally bad people, and there are SO VERY MANY bloggers that would do exactly this for free. I would keep away from them, especially as they messaged you first. This implies that they're messaging lots of other people too, to make money, and will not do your work justice. I honestly don't think it's worth it, not to mention that $35 is one of the highest prices I've seen for this type of thing.
Honestly, it's not a scam, but it's almost there. You do NOT need to pay money for this type of thing. The only time paying money is worth while is if you're buying an ad space and a post comes with it, but even then, ad spaces are overrated, especially on a sidebar, or on a blog that displays 20+