Replacing SS/HG Overworld Pokemon Sprites

[Screamo]

I've been searching a lot on this subject, but I've not been able to figure out how to do it.
I need to replace the Lugia sprite, but first I need to get the sprites so I can edit them.
I'm making a Shadow Lugia for the game
The only thing I need to do now is making the overworld sprites.

Sorry if this has been asked before.. I did use the search first!

Edit: I've finally managed to get the sprites from a website, but how do I insert them into the game once I'm finished editing them?

[Exaskryz]

Surely there are tools for this. Research narcs and nitro explorer, which are files and a tool used to extract and insert things into the game.

[ascension7]

It's quite a complicated and tedious process, but if you do it correctly the first try, it'll only take about 15 minutes. I made a tutorial video here:
http://www.youtube.com/watch?v=IanpeTRdp24
You can PM me if you have any questions. There's files (tools and such, and I think written directions unless I forgot to include them) in the video description that you can download.
As Lugia is a large sprite, the video doesn't cover those. Though I do include the slight differences in the instructions, such as the palette offset. Again, feel free to PM if you need any help!