here's an essentially useless piece of advice, which may drive you up the wall.
all methods here have advantages and disadvantages, but none of them will kill your computer, and there are easy way to iron out the creases in every case.
if you roll a dice, or close your eyes and point, or choose some other equally random method for choosing what to do, you'll be left with a path that won't require too much effort (but will require a little time), that will leave you with a really cool operating system.
me? i've always used the upgrade path.
(i'm the sort of person, when at a restaurant, if someone is having trouble choosing what to get, i say something 'helpful' like *pointing at menu without looking* "try this, it's really yummy". the mac os is a great restaurant, and whatever you choose from the menu will be cooked to perfection and very tasty

)