Cab rear floor crossmember

[AJLChase]

Has anyone had to replace this part of the underside of the floor? I finally got underneath my new truck and found that both sides of the crossmember have rust through. It doesn't seem to be contagious to the actual bottom of the floor pan but won't know till that piece is gutted out. Is this a hard piece to attach as I'm sure it's a job for a welder? If this is rotted out, how likely is it to spread and how soon should it be torn out and replaced? Also, if it's not too much to ask...what would be a reasonable price to pay to have a professional do this? Thanks!