It takes more than 15 minutes. It took me 3 hours total, but that included looking for the right allen wrench to get the TXV bolts, turning them 1/6 turn at a time, recovering the refrigerant, making up a hex socket to get the bolts on the firewall, and having a vacuum leak at the low pressure adapter for my gauges, and recharging the system. Other than that, it was a straight forward AC repair.

I haven't had to replace a TXV before, either. My e30 has the original and it has more than 500k on it. And multiple compressors. But I saw an episode of Rainman Ray's Repairs on the tube and he said if you have a TXV obstruction, and the compressor is still working, just change the TXV. Well, my compressor still works, I had a few free hours today, a blocked TXV is a pain to deal with on the interstate, TXVs are cheap, I didn't have time to change the compressor today, and I make a 100 mile round trip in this car every three days. Add all of that up and there really wasn't much reason NOT to try it. I'll know in short order if this is going to be a lasting repair or not.