Front site problem on old Remmington pump 22.

I have inherited my grandfather's old Remington 22. My uncle had restored it to safe shooting status. We were shooting it at the gun club's indoor range and the front site fell out of the groove for it near the muzzle. We have the piece with the gun. There is some slight rust in the bed of the groove (apparently superficial, but I am not a gunsmith). The gun shot well prior to that and we stopped shooting it after it fell out.

Questions:

1. Is this a newbie job?
2. Anyone know of instructional video or other instructions for how to fix this?
3. If this is a gunsmith job, is this a job for a regular gunsmith or is this going to require superspecialized gunsmithing?

Thanks