Seems to me that Russia is heading for another fiasco like their occupation of Afghanistan from 1979 to 1989. Mujahideen insurgents throughout that country made life for the occupying Russians a living hell.
I have little doubt that a Ukrainian resistance will be even more devastating to their invaders... and the insurgents' appearance doesn't set them apart from their occupiers.
There are big differences between Afghanistan and Ukraine.
The Soviets in Afghanistan and later the US and it's allies, might as well have been aliens from different planets.
Ukraine, while having very good reasons to hate Russia going back at least 100 years or more are more like each other and share ancestry and customs.
I believe they will have less will to resist, but I guess time will tell.