Irons and Lighting Conditions

One of the ranges where I shoot has really difficult lighting conditions. The 50 yard targets are really dark. The 25 yard targets are really bright. Depending on which point you get, you may have bright light directly on the sights. On other points, you may have almost no light at all.

I have a pair of Benellis. I bought both used. Neither included any extra front or rear sight blades.

Can someone tell me if the sight blades have different notches? Can you get different width front sights? How easy is it to change out the sights? Will the zero be close?

Thanks,
D