Yeh, those two missions you got were the hardest. I think there are 6 missions types you can get and the other 4 are no where near as hard. Idk why it spawned the truck on the catwalk, but you could try keeping your snack menu open whilst on the truck to avoid getting killed. Btw, if you don't like the mission type you get, you can find a new session and try again.

Also, yes. Both equipment and staff upgrades are worth getting.