Hi, i'm new to this car and not from the USA. I need some advice with replacement of the transmission of 1G GS 150hp. Sadly i am not able to find the same, but have found a lot of 2G GS ones. Are they direct replacement or should need something else to drop a 2G tranny instead of the 1G?

You need the trans codes of each trans. I am guessing you have a 4g63 na with an f5m22. Europe 2g cars non turbo also have 4g63. Check the trans code you have and of the donor car.

If you change to a 2G transmission, you may need to change the axles too due to length possibly.