Repairing a leak in a pressure assisted toilet can be tricky since the interior tank hides the parts that are most likely to leak. That being said, it isn't much more difficult to repair a pressure assisted toilet than a gravity flow toilet.
A leak at the tank bolts or the tank gasket can be repaired fairly easily once the internal tank is removed from the outer tank. One challenge you might face is finding the correct replacement tank to bowl gasket. Since pressure assisted toilets are not as commonly installed in homes as gravity flow toilets the repair parts are not always in stock at home improvement and hardware stores. You may need to go to a plumbing supply house or order the parts online. Once you have the necessary replacement gasket and tank bolts the repair can be done fairly quickly.
This step by step guide shows how to repair a leaking pressure assisted toilet.