Quick Question about iTunes

Ok so when I got a new Macbook and transferred all my songs from my mp3 player to my new laptop and then opened my songs in iTunes, it seems iTunes make a whole new folder for itself (btw I also had to completely customize my iTunes again with the right albums, artists, etc). What I want to know is:

Is it necessary to keep my original songs because it seems like iTunes makes its own copy of the song anyway with the right album picture, artist, etc?

Since you let iTunes copy songs to the iTunes directory, you don't need to keep the other set. You can delete those other songs to free up space.

When I got my macbook a couple of days ago I realised that my music was getting copied to itunes library and it was all "organised" etc in so many different folders so I deleted it and re-adding them to my library despite having to re-edit a lot of the tags again...

I keep my music on an external drive and mostly use my ipod for the music, saves space on the actual machine for me you see - but is there anything I can use such as a plug in for itunes that will write all the new info to the mp3's much like what would be written on the ones had they been copied to itunes library?

I spotted a thread that discussed this a few days ago but can't find it again - sorry for gatecrashing another thread but figured it was on the same lines of topic anyway!