Good evening,
Not really, the game tells you where each unit can be upgraded already. By playing the game a little you will quickly be able to tell where you can and where you cannot. Keep in mind that you can and should use the 'hide all units' button (H - shortcut) to have a better clarity of the map. You also can and should use the 'show tiles types' button to show the size of each urban tile.
You can disband units by either doing so through the Order of Battle, each unit slot has a delete button, or by selecting a unit on the map and simply pressing 'delete' on your keyboard (the DEL key)
What date was this? If it was 1945, would not be a surprise, the game ends in 1945
Except you, nobody said anything about campaigns ending early so I'll take it as you're not experienced with the game yet