How much you need to disassemble will depend on the suitcase you have. I had a Birdy Classic, that I packed a few times into a borrowed 29" Samsonite and later in a cheapo semi-hardside case I bought. For both I needed to remove the handlebars (if you have a adjustable stem that would be easier, as it should just slide out), take out the seatpost, and remove both wheels. I removed the pedals, derailleurs, and axle quick-releases also. The wheels need careful placement to protect the frame (and the wheels) - you'll need some foam or other padding or something to put between frame & wheels. It's not a difficult process, but it take a little while (30-40 mins?) and there are guides with photos online.