You can test your Redirect by using Live HTTP Headers for Firefox. It will tell you in seconds whether it is a 301 or 302 redirect.
Yes, the underscores can be replaced with hyphens.
What is the maximum number of underscores there will ever be in a URL?
Whatever this "Redirect" actually turns out to be, and now that you are using RewriteRule on this site, you must also change this "Redirect" rule to use the RewriteRule syntax with the [R=301,L] flags.