I've done it a couple times. It's an easy job.
The cord usually has a plastic strain relief around it, where it goes into the chassis. Squeeze it with a pair of pliers from the inside of the chassis, and you can pull it right out the out-side of the chassis.
The hole in the chassis is usually big enough to allow you to put in a new, larger diameter cord without cutting any metal. I recommend the Volex 17617, made of Belden 's best power cable, but replace the molded plug with a Pass & Seymour 5266-X. Of course, this is a captive solution.
If you want to put in an IEC, get some chassis nibblers and open the hole with them. Schurter 6100.3100 is supposed to be a great IEC chassis mount. I don't know, because I use Neutrik Powercon instead.
When you're connecting the new cord or IEC, observe the same polarity. If you're replacing a two-conductor ungrounded cord, just connect the ground to the chassis with a screw.