Need specifics about mod_proxy for blog domain and 301s

[SL_SEM]

I am getting the IT staff to move our blog from "blog." to "/blog" using mod_proxy for apache, but I had a couple of questions about this I was hoping someone here might be able to help with.

Is it correct that just setting up mod_proxy will make the blog available at both URLs? the "blog." subdomain and the "/blog" folder?

If so, what is the best way to 301 redirect all traffic from "blog." to "/blog"?

I assume this could be handled with a blanket 301 style rewrite, but I wanted to get some other opinions before getting with my IT guys to do it.

I am technical enough to talk about this, but not do it myself, so experienced opinions are appreciated.

Thanks!