tcoop25 I would check the shock oil and diff grease. The fuel lines probably need replacing too.
Im pretty sure you can use that flywheel and but I think you are going to need a pilot nut for that shaft. Id get new clutch shoes too since the old ones are probably worn and youre going to want good shoes to go with that new engine.
You should be able to put the 100cc tank on there without a problem
This engine mount will work fine http://www.hpieurope.com/piw.php?lang=es&partNo=86000
This is the air filter I have on mine http://www.hpieurope.com/piw.php?lang=en&partNo=87207

Welcome, and never worry about asking questions. There is a great group of knowledgeable people on this thread that are always more then willing to help out.
Post up some pictures as you do your upgrades.