rear oil seal replace without removing engine or gearbox

You either have to drop subframe to remove transmission, OR try to lift or pull engine and tranny as a unit from the top. The tranny doesn't have to come out completely but you have to separate the engine/tranny and support them with some type of brace. The factory manual recommends dropping transaxle out the bottom. The other repair guides (Haynes, Chiltons) suggest pulling engine/tranny as a unit out the top. Either way will require a lot of work, and if pulling tranny may as well service CV axles. Only other option is to add some type of stop-leak oil additive and keep an eye on oil pressure and level.

The rear main seal is a one piece seal so there is no way to replace it without separating the engine and transmission.

and do the tranny seal if it's an automatic , check clutch if it's manual , might as well do it if you have it out