does combat include a standard odds-based CRT or some other combat resolution mechanism
Other. Infantry & MGs all have Gunfire Factors. Add up all GF involved in an attack, find appropriate column on inevitable chart, apply modifiers (there are many - and that's a good thing) and then count the dead.
Only the melee (close combat) table uses odds.
Do leadership and morale play a part in the game?
Absolutely vital, yes.
Is there an overall campaign
No. There exist a handful of campaign games in the system but there are none involving Stalingrad at this time. What you've described would be more the domain of a higher scale than squad-level, as these maps depict a rather small portion of the Stalingrad area.