The gas axe is your friend if they don't want to budge (or blow torch). I spend a lot of time working on old engines (50-80 years old) so I know all about bolts that won't budge LOL
If by chance the bolt DOES snap and your are left with the stud being stuck in the block then you have a number of options. (I don't want to teach granny to suck eggs, I just don't know how much you know so I'll say it as basic as I can)
If the stud is protruding a little bit use a set of mole grips to clamp on to it and try and twist it out with them. If the grips keep slipping, try filing down two opposite sides of the stud and clamp that (or possibly use an open ended spanner if one will fit). If there is no protrusion then you are best drilling it out. The best way to do this is to get a punch, and punch the centre of the bolt, then drill a hole thru the centre of the bolt (the punch hole is just so the drill doesn't slip to the side when you are starting your drilling) then use a stud extractor to remove it. If you don't have a stud extractor and don't want to buy one a garage will be able to do the job quickly for you.
When you replace the bolts on the fanimold wipe a bit of copper grease on the threads so the next time they are taken out (by yourself or the next owner) they will come out much easier.