2003 siverado 2500hd-when i put on the left turn signal-the 4 ways go on.how big of a problem is this and how much should i expect to pay for the job.

Multi function switch ( signal switch assembly ) is bad .. most part stores carry after market now and they really aren't that hard to change. I would expect around $200.00 for the part and 1.5 hours to change. If you are fairly handy you could pick one up at a salvage yard and change it yourself and save quite a bit.Once you remove the plastic column cover and the tilt lever ( it pulls straight out ) there is one screw holding the bottom that you will need a torx bit and a 1/4 drive wrench to remove so you don't have to pull the steering wheel.
Hope this helps.