has any one replaced the gasket and was it reasonably simple to do?

Hello the head is made of aluminum ,it is a over head cam the timing belt will have to be disconnected.
The head may be dis-formed by heat it may require rectifications.This engine may have wet liners their gaskets could be also burnt.

Pistons may have damaged the liners when it over heated.
If this is the case it would be more economical to replace the engine.
First thing the head to be removed to have an idea on amount of damages.

l do not reccommend doing this yourself unless you are an experienced mechanic. The surfaces need to be perfectly leveled out in order to avoid leaks. And the metal get distorted with time, that means that you will need to use special tools/machines to level it.

This can be an expensive repair, get a few quotes and then consider what to do. It can be cheaper sometimes just to find a used engine from a salvage yard.