Regarding the master link, I'd suggest you use one simply so it's easier to take the chain off for cleaning. As for chain length, as long as you have sufficient slack in the chain with it on the largest chainring and largest rear sprocket (you may never deliberately use that combination, but if you shift into it by accident and the chain's not long enough, you'll break something) that's fine, although you may have some slack if you use the small-small combination (which you shouldn't use either on account of cross-chaining).

As for adjustment, read the Park Tools article on the subject, they explain it very well. http://www.parktool.com/blog/repair-...nts-derailleur