Using proxy_redirect correctly

Hi all,
My proxy seems to be working, at least so far. I browse to
sd2.mysite.com
and find the OSTicket installer. Since I’ve removed the OST site from
Nginx, I know Apache is kicking it like it should be. The only problem
now
is that OST thinks its location is 127.0.0.1:8080, which is the internal
redirection but not what I want it to use.

I know I have to use proxy_redirect, but I don’t quite understand how
this
directive works. I just tried:
proxy_redirect 127.0.0.1:8080 sd2.mysite.com;
but that didn’t work. I find the documentation I’ve read thus far to be
rather confusing. All I want to do is replace 127.0.0.1:8080 in any URL
on
this site with sd2.mysite.com. Do I need some kind of regular
expression?
To move this proxy somewhere else (currently it’s in location /
context)?
Should my proxy_pass also be moved to a different context?