Hi there Delta, welcome to the forums! This is a great place to vent your frustrations (I have, many times...)
The Haynes manual is OK - but like for most other cars it can be a little vague at times.
As Lag quite correctly states the head skim process is a pretty cheap job it literally "skims" a fraction off of the surface of the cylinder head, so that the surface is perfectly flat before offering up to the engine block with a new gasket.
Lag is also right by saying the 1.6 energy engine is a good 'un. A friend of mine has an R reg Megane with well over 150K on the clock, and the engine is as it was when installed at the factory (aside from servicing!) And it runs as well as it was new. It seems that there were some duffers (mine being one...)
A garage will normally quote around 300-400 quid for a head gasket replacement. If the heads gone (ie cracked) then you're looking at £750+VAT from Renault for a new head. Scrap yards are not forced to sell you a used cylinder head as they are then left with the bottom half of a used engine which is pretty much useless to them. The head gasket went on my Megane (again!!! but due to the water pump, apparently) a short while back and I managed to source a second hand head from
. Lucky find methinks! I still have the old head, cleaned up in my house, it's a conversation piece, useless in a car as it has cracked. I did the swap myself, with loads of help from me Dad, who has done a few head gasket jobs in his time (he used to really love Austin Maxi's!)
Don't give up on the car, these old Meganes are great little cars and look at them today compared to the competition. Contemporary Astras, Escorts and 25's look well dated today where I feel the Megane's still look fairly fresh - and the handling with the crazy amounts of body roll but incredible grip (even with cheap tyres) is great!
Anyway, sorry to go on for so long... Keep us posted, I hope you get it sorted one less Megane on the scrap heap. There are loads out there that already have been.