GMC Repair: Turn signal noises, multifunction switch, signal relay

Question
I have an intermittent problem.  There is a noise that sounds exactly like the turn signals happening once in a while.  There is also a sound similar to an electrical circuit arcing.  Neither is continuous.  I changed the turn signal relay under the dash...did not fix the problem.  A local shop said it is a multiswitch problem and wants $380 for the switch and $140 for labor.  How do I confirm it is a multiswitch issue and how hard is it to replace?  Thanks!

Answer
does it do it randomly while driving down the road?  I have a 99 Jimmy that was doing the same thing and it was the multifunction switch.  Kind of a big job, lots of wires and panel removal is necessary to acces it and replace it.  $140 labor is pretty good if you can find the switch for cheaper, i have seen them on ebay for around $100