OK, these are pretty simple. For the first one, make an event that is your shopkeeper.
Set it to Action Button, and in the events select 'Shop Processing' (I think it's on the third page)
Now, add all the stuff you want him to sell.
To add a tileset, import it into your game like a normal resource. Then, press F9. Under the 'Tilesets' tab, increase the maximum number. On one of the new blank spots, fill in the details you want, select the tileset graphic, set the priorities, and you're ready!