First of all I am very sorry for your loss.

I guess your wife passed away in Nepal. So can you get a death certificate from your village woda? You can then get it translated officially in one of the government offices.

Regarding your marriage certificate, you can get one from your village woda signed by woda sachib. If they can do it in English that should work if not you can get that officially translated as well.

You don’t have to travel to Nepal. You can ask your relatives to get it from the woda. Hopefully they won’t ask you to be physically present. I don’t think they would.