How is the Ukraine going to keep the wide variety of vehicles operating? They are getting everyone's old vehicles, but do they have the spare parts, supply system and people to replace the parts? A lot of these vehicles are going to left in a field somewhere.

they can and do use disabled vehicles for spare parts. With BMPs it's no problem, they have the experience and the tools. With M113s it will be more difficult, but it's still a mechanical vehicle, no on-board computers.

The Ukrainians won't have maintenance problems with the 113s. They'll use them for a couple of months and then throw them away. They were designed to be expendable battle taxis, anyway.