I have done the ziplock bag method before and it works like a charm. I usually doomed in 3 gall batches, put it in an ice bath, add 1 gall frozen, and then 1 gall that sat in the fridge over night. My batches usually chill to 70 degrees in about 5 min that way.
You can brew just about any type of beer with both methods. The only real difference is with extract you buy either powder or liquid extract and all grain you make the extracts yourself with the raw grains. Extract is far easier ( and faster) is you are just starting out.
That is very true and a point missed. Checking out local brew stores is a great way to start, some offer beginners brewing classes( that's how I got my start). Another book to take a look at is "How to brew" by Jon Palmer. Between the class I took and that book I have not brewed a bad batch yet...
Are you looking to test the waters and do extract beers or are you looking to jump on with both feet and do all grain? This will affect what you need to buy.