Hi,
1. Where can I buy supplies in Whiterun?
2. How do I buy a house in Whiterun?
3. Can I get a replacement for Lydia if she dies?

Thanks!!

There are two Smiths right near the main entrance at Warmaidens, they sell weapons and armor. There is also a Smith behind the Companions hall.
There is one Alchemy shop right on the market place, they sell ingredients, potions and recipes.
Then there is a general goods shop that sells a lot of random things next to the Alchemy shop. I think it's called Belethors.

You have to progress so far along the main quest and you will be offered the chance to buy it for 5,000 gold.



You can get other followers but Lydia will not come back. There are a lot of potential followers in Skyrim that you can use.

1. In a store (don't tell me you can't find one, there's one right near the entrance, you can't miss it.
2. Ask the advisor of the Jarl.
3. You can reload or choose between many other companions.

You could figure that out yourself.