1. This is a very archaic phrase -- as you probably already know.
2. This is probably the only place you'll ever see the word "stead" used. It means something like a place or a location.
3. So, "it will stand [me, you, he, us, them] in good stead" means "it will put [me, you, he, us, them] in a good place":
- Your knowledge of English will stand you in good stead.
- Their politeness will stand them in good stead when they visit the Queen.
4. Again, super archaic.