Will I be able to understand what the hell is happening or should I go back to the first two?

" Will I be able to understand what the hell is happening or should I go back to the first two? "

Use an emulator and play the first two.
 
Unless you're against that kind of thing.

Just pile into the game, you will be just fine.

The first one is good enough that playing the game is worth it, I thought the second one's lack of direction in the over world to be a little too confusing for my tastes though. 

" Use an emulator and play the first two.  Unless you're against that kind of thing. "

yes, i am playing dark down and it has this   particulary   thing in which while the characters talk about other characters or important stuff from previous games the text appears underline so you can touch it with the stylus and in the top screen appears a small summary of it. 
 
sorry for the english, i speak spanish lol