I always use Valvoline 80W-90 gear oil in my B2200 5-speed transmission. And in my 2 Frontiers. and in my 1971 VW. There's a pump that screws into the container, get that too. Don't fill through gearshift, that's tacky.
Oh yeah: drain and re-fill that differential too. You might need a 23mm socket too, got mine at O'Reilly, guess it keeps my 21mm, 22mm and 24mm sockets company....don't know why manufacturers can't just use common sizes....