The part you have marked Y1915 is a timing crystal running at 24 MHz. It does look like its got some corrosion damage along the left edge as well as some areas around it. This crystal is used by the CPU as its clock so loosing it would be a big problem! So you do need to clean this up and you may need a few new parts.
As far as your WiFi problem, this is not the cause. You likely need to do a bit more inspection looking for more corrosion damage.
While this might be repairable, the amount of effort maybe more than it’s worth. If this is a 1.3 GHz 4GB board I would just replace it with the 1.7 GHz with 8 GB of RAM board as being the smarter direction [product|IF188-095-2]