Firstly, welcome to the forum. I agree with Andrew, don't panic. When I was first diagnosed two years ago, I joined this forum, the help and support you get is fantastic. Just talking to someone else that has the same problems and issues can really help.
Secondly, I know how scared you must feel but try not to fear it. I was diagnosed two years ago with mild keratoconus. I frequently use my computer for University assignments and for searching the net etc. I have been told that computer use doesn't seem to have much link to keratoconus, as Andrew pointed out.
I first noticing my condition when I started struggling to read lecture powerpoints. I was diagnosed a week before my main final exams. it was extremely stressful. I was given my glasses the day before one of my exams. I had never worn glasses and boy did I struggle with them, I struggled to walk in a straight line with them! (I'm pleased to say that I even managed to ace the exams somehow). My University has been fantastic in supporting me. I have been offered alot of help.
I still wear glasses for my condition and it doesn't really bother me, I love my glasses and I've been told they make me look quite handsome and intelligent

As for your other questions, I suggest you do some research on the internet, that's what I did. Like Andrew said Keratoconus can be unpredicable but most of the time it can be controlled so don't go worrying. I also agree with Andrew, check out some of the leaflets.
If you ever want to chat, give me a private message. I'm always happy to lend an ear and answer any questions you may have.
Remember DON'T PANIC!!