Has anyone ever gotten a labour lawyer? If so, how much did it cost?

My workplace is garnishing my wages now that I've put in my notice. I never signed anything saying I would pay back my signing bonus from 5 years ago and everything else they paid for was a gift (I kept the emails). In fact, the signing bonus contract says I only need to pay it back if I resign before a certain date but that date is long past!

They want me to pay back over $8k!

Is it worth it to get a labour lawyer involved? Or will that cost me more? I'm just worried that I'll be out the money they're garnishing AND lawyer fees.