I can't say it's easy to get Shiny but Dratini are found in the dragons den behind the last gym.
None, DRATINI EVOLVES BY LEVEL (30)
To get a shiny Dratini in Pokemon Crystal you need to find one in the wild or hatch one. This is extremely rare though with a 1 in 8192 chance of the wild or hatched Dratini being a shiny. There is no way in Pokemon Crystal to improve these odds.
Its easy, all you need to do is catch Lugia and the 3 like entei then take them to the dragons den, surf, then catch a dratini.
in dragons den you can also catch dratini's in there
I believe you can get a Shiny Stone in HeartGold in the Pokèathlon Prize Corner after you get 5000 Points.