here’s the (Russian for now) video for Individual missions. English subtitles are available.
Notice how Wargaming plays the “this tank is a reward only for skilled players” angle. Well, it might certainly be true to some extent, but the first set of missions for StuG IV doesn’t seem that difficult. The important part is that if you don’t manage to fulfill both primary and secondary objectives, it’s possible to re-select the mission and try it again.
Oh yea and the special girl crew perk activates only in girl-only crew, it does NOT mix with BIA.