I am pretty sure that you can not use a 1g trans in a 2g. Well it will but it is far more work then it is worth I believe the 2g trans is better then the 1g anyways. As far as a performance trans that would depend on your set up if you need it or not. Welcome back to the game sounds like a good...
While you are at it getting a trans temp gauge to monitor your transmission with would be a good idea too. Running a 16g you can brake boost at the line and take off in boost. Also look in to a shift box. Roadsurge just came out with there new model and I have heard nothing but great thing about...
Brake boost on the stock converter depending on your set up you should be able to build boost on the line. On a 16g the stock converter works great, when you get into larger turbo set ups is when you would need to think about getting an upgraded converter.
As said by others you are gonna need to get bigger injectors, a wideband, and a way to tune before you turn up the boost, this is also assuming you have a boost controller.