The squeak during gear changes may come from the forward clutch (this is a wet clutch that is enaged for all 4 forward gears). Is this squeak present when pulling away from rest especially uphill? One way to determine the condition of the clutch is to perform a "stall test". Engage first or D and apply the foot brake firmly with the left foot so that the car can't move (do this in an area where there is nothing in front that you can run into just in case the brakes are substandard), then press on the throttle. If there is a pronounced sqawk or judder then this is due to the forward clutch slipping. This is usually due to worn clutch plates although it may also be due to low oil pressure (check the oil pressure at the plug on the filter head (100 psi in all forward gears, 150psi in reverse). The problem with these gearboxes is that spare parts for them are becoming a bit like hens teeth. Changing the clutch plates, if you can get them, involves significant dismantling of the transmission once it has been separated from the engine.