No noises and no tears in the boots may suggest the mechanic was doing his best to up-sell you into some "preventitive Maintenance".
I have replaced my half axles myself and it's not too difficult of a job, you will need to borrow a gear puller to drive the axle back thru the hub. Try one of the big chains, Autozone or Checker for a price on a reman half axle, it usually has to be special ordered but they will lifetime warranty it for you and it should go about $100 plus a core.
Good luck.

John Sullivan