Rimmers have new screens available
https://rimmerbros.com/Item--i-CMB101120PMH
As for doing it yourself, I've done mine own in the past, not on the MGF but the procedure will be the same, As well as the screen you'll need a pull wire to cut out the old screen and the bonding agent for glueing the new screen in, I'd watch a few youtube vids to see if you think thats something you'd be happy to tackle.
Also worth checking your insurance, Most policies don't have any excess for windscreens, nor effect your no claims, obviously that would be on a non repairable crack