I believe Scag has original owner warranty only. I copied this from their website
Warranty time periods are from the date of purchase, are only applicable to the original owner and are non-transferable.
I had a landscape trailer with a wood floor that always had funky brakes and couldn't figure out the problem until time to replace the treated floor and found a bare wire between the wood and frame.
If you have gutters you need the guards otherwise the weight of the ice and snow will pull down the gutters.
As far as installing them it depends on the roof panels and how much snow you get. You would probably be better off with a bar type system.