From your description the 30 inch barrrel is a fixed choke configuration. Again, you should check to see if ok to shoot steel shot but lead should be no problem.
With the Accu choke barrrel I assume you have a choke installed. With the gun unloaded and safe take a look at the muzzle and you should see a screw in choke. Assuming you do, you need a choke wrench to remove it and see which choke is installed. Depending on maintenance the choke may be difficult to remove? Hopefully not. Again, if memory serves me well those barrels originally came with three chokes (improved cylinder, modified and full). Again, check the Mossberg web site. There's a link in a post a couple of days ago to their barrrel selection site.
Regards