Since I'm too lazy to learn VI properly, can someone tell me how to enter the following commands?

edit/open a readonly document, for example a repository list file

delete text in a file (sorry, I'm stupid ;p)

save changes made to a readonly file

Of course once I start editing a readonly file it would mean converting the file to read/write...

All in all, probably not hard to do but I'm still learning the ropes. Thanks in advance.