1) Is there a difference between Modding and Flashing? What are the advantages? If I won't be using xbox live, does it matter one way over the other?
Modding/Flashing is the same thing. Just different terms.
2) Replacing the HDD, whats the biggest HDD you can put in there, what are the requirements, are there only certain drives that work? When installing it do you have to set anything specific up?
120GB It's damn near just as cheap to buy one now days used off eBay.
3) If you want to put the games directly on a Drive instead of on DVDs how is this done, are they iso or a certain xbox file format (which im assuming its a special xbox file format just dont know the name). Can the xbox read the files from a portable drive? If not can you copy over the games from a portable drive to the xbox harddrive?
Still requires you to have the disc. No it can not run games off a portable drive neither.
As you can see I am very new to this and any information would be very helpful.
also, if Flashing is different than modding, and you have to mod, what is the best solderless modchip to use? Do they work with all xbox versions? Thanks again!
Depending on what kind of drive you have depends on if your going to need to buy any additional hardware. (CK3 Pro, Spear/Probe) It just may be cheaper and smarter for you to send it off to a professional.