How do modify the dashboard and new post pages

So I guess this is a broad question but Im trying to do a couple things here.

1 – I want to add a couple custom fields to my new post page and have the input added to the wp_postmeta table.
2- Then, Id like to remove features from the text area part of the new post. I only want users to be able to add pictures with it anyway. I WAS editing the global.css file to display:none the stuff I didnt want but I was told not to do that (also I dont know how to package that in a way so if people download the theme they could easily replace the file)
3 – Id like to have a secondary custom post function on my dashboard.

If I can just get some links to examples or maybe a little code I think I should be good. Thanks!