The threads you are referencing are about an X5 diesel. The diesel 3.0 had much more torque, and experienced a relatively high number of failures with this particular transmission. BMW subsequently switched over to a stronger transmission for the diesel. I don't think that the diesel transmission failure rate is applicable to your 3.0 gasoline engine. I think that the general information about that transmission contained in RRPhil's excellent posts is very good.

If you are not going to be working on it yourself, I would find a good independent transmission shop familiar with this model of transmission. I would ask them to diagnose it, specifically referencing the 1-2 shift issue, and would lean towards trying a valve body repair or replacement (if that is what their diagnosis pointed towards) before beginning a transmission overhaul. If they can't find a likely cause, I would consider a transmission overhaul of my own transmission (not an exchange).

I can't point you at a specific likely cause (other than the solenoid and accumulator spring associated with the 1-2 shift) but I would be trying to test that circuit before removing the transmission. The fact that your fluid isn't burnt suggests you don't have a problem with clutches slipping, but rather with a single circuit relating to the problem shift. All in my opinion.

I wouldn't change the fluid on the faint hope that that would resolve the issue, but it is a gamble that you may want to take based on your own cost/benefit evaluation. It is certainly the cheapest place to start.

Hope that helps. Good luck.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue