The exhaust turbine is an integral part of the shaft, it cannot be removed. The hex is provided on the turbine so you can hold the shaft while tightening the compressor wheel nut. The shaft should slide out toward the exhaust side once the compressor wheel has been removed. Seized or coked bearings can make this difficult but be careful, the shaft is easily damaged. It's been a while since I've had a turbo apart but I believe once the shaft is out, the turbine heat sheild and the compressor backing plate are removed the thrust washer, the circlips and the bearings can all be removed quite easily.
Balancing is not a must IF the turbo was balanced as seperate components. Most older turbo's are balanced prior to assembly. These turbo's will have material ground off of the both the turbine and the compressor wheels and nothing ground off the compressor nut.
Newer turbo's tend to be balanced after assembly, this balance is lost when the turbo is disassembled. You can tell if a turbo is integrally balanced by looking at the compressor nut. If it shows signs of being ground on one side for balancing, chances are the turbo was balanced after assembly and will need to be rebalanced.