Right now I am at the stage where I can say present tense actions. I can't do future/past since the book has not come to that part yet. I am fairly good at 2 of the styles of speech, with the third(informal) coming along a little slower.

I'm not trying to sound like an @$$, but I heard this was one of the most difficult languages to learn, so I wanna know if the curve ball will hit me later on or if the book is hiding the difuculties until later.

I study everyday 2 hours minimum, but usually 4-5 hours a day.

If you can speak only in present tense, you probably are at the speaking level of a child. So yeah it gets harder (present tense is the easiest tense in any language).

Does the conjugation change when in the past or is it just memorizing different words to use before the verb? Same question for the future tense.

The conjugation changes. It's all about memorizing the root of the verb and then adding different endings.

it gets difficult in stage 4 where you have to jump on platforms that fall after awhile while trying to dodge killer fish that take away your life points and if you fall in the water, you die automatically.

^ lol, I was thinking the same thing.

So just throwing this out there, I would not say "Im Ne Da" for a past tense action?

$hit, when does it get easy, that's what I want to know.

<_<

Maybe I am just smart.

You don't say "Im ne da" unless you're trying to fake a North Korean accent.
Past tense version would be "it sseot seumnida"

I guess learning vocab and idioms would be the hardest part.