Unfreezing is a relatively easy process. They'll send you a pin where you can do it online, or you can send them a letter. It'll take them about 7 to 10 days to unfreeze things
As a side note, if you use the online instant unfreeze, note that at least one of them (I can't remember which) handles timezones extremely poorly, and if the "start" date of your unfreeze has passed in their home timezone, they'll reject the unfreeze with an extremely vague error. You can resubmit using "tomorrow's" date and it will work fine (and be unfrozen immediately).