The spindle isn’t hard to change on these trucks. I had never done any sort of front end work until last year. Though I know enough to be dangerous, it was not something I would consider difficult.
@someotherguy laid out pretty much how I did it and I didn’t even look anything up prior to that. I did put a jack stand under my LCA while I worked on other parts of the front end. This kept the spring in place and I didn’t rely solely on the floor jack.
The mechanic may be right, it’s hard to say without being there or without seeing a very well made video of it. However, I think a lot of good info has been shared here advocating for a new used spindle. Hell if you want new you can buy a brand new one from Rock Auto. I’d probably grab a used one only after comparing to the other side and cleaning the surface with some emery cloth.
You could always blow the other side apart and see how that bearing feels and looks. Compare the two and let us know.