Hi LCSPD,
In regard to the OpenIV issue, you can safely ignore this. It will have no impact on the model in game at all.
For the tinted windows, you will need to change the tint. You can either do this is game, via a trainer, or you can edit the tint in the Vehicles.meta file. To do this you'll want to navigate to mods\update\update.rpf\common\data\levels\gta5\vehicles.meta and then to the Sheriff2 section. You'll next need to change the tint colour. Simple change the Diffuse tint line so that it looks like this: