Please excuse my ignorance; the only other car I've replaced a head on was my late FrankenCamira, a JB with a late JD engine ... a very different beast.

It seems I have a cracked head in my EL Fairmont Ghia, which a bottle of goo sealed just long enough to confirm the rest of the engine seems okay. No coolant in the oil, no oil in the coolant, just steam in the exhaust which disappears when I take the #1 sparkplug out, and an over-pressurised cooling system.

I've managed to obtain an okay-looking stock EL head, complete with camshaft, which supposedly only had about 5000km on it before the donor car was killed.

I don't need super performance; I'm a (mostly) sedate driver who simply wants a comfortable barge on LPG to drive to and from work. And money is tight, hence the desire to use what I can get cheaply.

Questions:

Is the stock EL head and cam likely to work reasonably well with the existing Fairmont Ghia ECU? I'd prefer not to have to pull the camshaft and valve train off what's supposed to be really low km head if I don't have to.

Are there any physical differences that matter between the standard and the red rocker cover - will the red one fit on a standard head, or do I need to source a standard one?

Any other gotchas, or other things that are worth doing at the same time? I plan on replacing normally inaccessible hoses and the cap, rotor and leads while I have it all apart too. And maybe the coil too, although that's not quite as big a nightmare to get to from underneath.

Just stick the Tickford cam into the stock head, easy to do.

Rocker Covers are the same, one is red and one is grey.

Chances are you might find when you take the rocker cover off that one of the forward headbolts has sheared off the hex head, so there mightn't be any thing wrong with the existing head.
Either way, good idea to have the gasket face machined before fitting.

Oooh ... that hadn't occurred to me. Here's hoping, because I just had another look at the head I picked up, with a different set of glasses and under different lighting . No signs of cracks, but it looks like it's been on for a bit more than 5000km and looks like it had a bit of gasket seepage now I've looked at it under different lighting conditions - and a bit more corrosion than I'd like around a few of the water passages. I think I'll pull the head off my car this weekend, take a look over it, maybe see if any local friends-of-friends who might know these engines can cast an eye over both of them, and take it from there.

Yeah, pretty rare to see a 2nd hand head around this era with only 5000k on it, usually BS claims.

Cracks generally occur between the combustion chamber and the exhaust side, usually bit hard to notice, and will come up on a pressure test at a head shop.
If it's only a head bolt, your existing head should be okay with gasket face machined, and you do your prep and fitting work properly.