Hello LDR812, I had a 178 and it had a gearbox rumble/rattle like yours and neither I or the MF mechanic worried about it. Rattly gearbox at idle in neutral is an MF characteristic.
Power steering, as 1 poster said, there is NO dip stick. Fill until the power steer oil runs out. NOTE if you are loosing oil and there are no EXternal leaks, then you have an INternal leak via the seal where the power steering unit mounts to the engine, or the input shaft(p/s) seal.
Power steering: due to the design used it is strong/light 1 way and weak/heavy the other.
Adjustment: MUST have some slack or no power steering. Get a service manual. I recall that there is a trick to getting the adjustment right.
Changing fuel filters: prefill the filters then fit to tractor. NOTE there are 2 O rings at the top of the filter, it is very easy to get a twist on the square "O" ring. Done right you can fire up and not have any hand priming. Ihad a CAV injector pump on mine and it had 2 bleeders. Also if bleeding fuel and you have reached the pump then crack a line at the injector (easiest to get to) this speeds up bleeding.
Check prices before you buy other service manuals online. Also purchase the "packet" not the "assembly". The assembly just includes a VERY expensive binder, otherwise no difference. These are same manuals sent to dealers, a very complete manual, it is not the I&T manual reprinted and sold by most others.