The balancer is held on by 6 or 8 bolts which are deep in the pulley. You will need a small mirror to see inside the pulley to get at them. Like larry said mark everything with paint so installation is easier and correct. I just removed the pulley/balancer on my 420 a few weeks ago and (also a 126) and got a few tips. Make a stud finder to make replacing the pulley easier. The stud finder is a bolt of the same size as the six holding on the pulley, but longer and with the bolt head removed. Screw this bolt into the top most screwhole by hand, hang the pulley onto this bolt. This will align the pulley bolt holes and make it easier to start the other bolt holes. Your gonna have to remove your stud finder bolt by hand so dont screw it in to tight. As you see its a very small space your working it.
To remove the balancer I used a rubber mallet and pry bar. On my 126 there was a waterpump bolt at about 1 oclock. I used the head of this bolt for leverage for the prybar. Gently apply some force to the back of the balancer then turn the crankshaft a tad. A little more pressure, then turn the crankshaft again. Continue this till youve got the balancer off. I got the balancer off in less than a minute. I read stories about guys spending two hours trying to get the balancer off, not believing it actually would detach. I figured there had to be an easier way. Remember, when you re-assamble your need to turn the engine back to TDC or wherever you began so make sure everthing is marked well.