Simplest way of removing OpenWRT?

A coworker gave me a Belkin RT3200 that has OpenWRT on it. Apparently it "didn't work" so he replaced the router. Is there a way for me to dump OpenWRT and reinstall the OEM firmware? As far as I can tell, the "factory reset" options in the Belkin manual don't remove OpenWRT, and the firmware upload options in OpenWRT seem to expect only a new version of OpenWRT.

Bearing in mind that I am a computer-knowledgeable but not at all hardware/networking savvy home consumer, is there any not insanely complex method of wiping this box and starting over with the original firmware?

Then again... maybe I should just leave OpenWRT on there? I don't know diddly about it. I'm used to the stock firmware on my Archer C7 and was just interested in the Belkin because it's newer by about 7 years. :)

UPDATE: I flashed OpenWRT to the newest version on the two Belkin RT3200s I got from work and successfully replaced my home network with them yesterday. Full 5G from the basement to the attic with only a few slow spots far from the router. Only real hiccup was having to turn the "allow shitty old connections" switch on the main one so that my old Epson Artisan 730 could still get on the network.