Mate, I'm all for people doing things for themselves but you're worrying me
![Shocked :o](http://forums.sohc4.net/Smileys/default/shocked.gif)
This is one of those jobs that once shown you'll be able to do no problem in the future. Easy, but also vital to get done correctly. You don't want that chain letting go at speed.
That said, I can't imagine you've done anything that can't be rectified. If by 'overtightening the link' you mean you've just compressed the side plate more than it needs, then yes just dismantle and start again. Hopefully you won't have damaged the seals (x-rings). If you seriously believe you need to cut it off then I can't imagine what you've done! The side plate is probably just binding on the pins where it's gone on slightly cocked - patience and judicious use of levers/ screwdrivers/ WD40 should do it.
When it comes to rivetting the pins, make sure you have the correct tool. Plenty of videos on YouTube showing how to do this, or better still have someone show you if it's your first time. Good luck, all part of the fun!
![Smiley :)](http://forums.sohc4.net/Smileys/default/smiley.gif)