Patching and Plastering - Studs seem non-existant,help

I read through the section on How to repair old walls where the plaster has come away from the wall. At one point it says if the hole is too big, fill it in with drywall, tape it and plaster over it. My problem is the studs in this very old farm house are 28" on center and not necessarily 2x4's either. It was built out of what ever they had on hand. Can I just screw it to the lath? I've comtimplated burning it to the ground and starting over fresh but that's too much work too.:D
When you say plaster what exactly do you mean? I've checked out plaster online and it came back with a number of types. The only plaster I can find at our local homecenters is plaster of paris, joint compound and spackle. Is spackle the same as joint compound? I bought a tub of spackle that goes on pink and when dry turns white. Takes away the guess work.
Is there anything I need to do to the walls before I do this? Will the joint compound stick to the old plaster so I can paint? Do I need to prime the walls with something first? I know I need to prime before I paint. I like Zinzers 3 & 1 Bins. Think that's what it's called. Stinks like hell, ammonia clean up.
Before they sell houses like this they should also sell you a manual on what to do with it once you own it. I know, hire a professional, wish one came with my mortgage book. :rolleyes: