Manual trannys have a drain plug at the bottom & a fill plug alongside the axle. Drain & put the plug back in. The 'crush washer' is an aluminum washer for the plugs, just like the engine oil drain.

Fill thru the fill hole, the proper level is right up to the hole. Once it has time to run down into the gearbox, the proper level is when it just starts to spill out. The only special apparatus I can think of is a tube that you can stick into the fill hole, or maybe a funnel with a tube on it.