looking at a 951c

I am looking at a 951c loader it has a rebuilt engine with about 10 hours on it since rebuild runs good but it has been sitting outside and not run for about 4 years it moves but I checked the trans and the rear end levels there is milky oil in it if I just change it will that be good enough or will there be problems with the trans tracks about 60% thanks jim

looking at a 951c