so hey basicly im new to the modding scene and i decided to use a different type of screen than the psone screen and it will use seperate power than the n64. if i were to use the two cannon bp-911 batteries to power the console alone (using the step down regulator as well) would the 4 amps damage the n64?

Amps don't "damage" a system. The system and screen will only pull the current needed to run it. For an N64 and a screen that is around 1A. So your 4A batteries would run your N64 and screen for around 4 hours safely.

thanks! good to know ive just recently have started learning all of this! thanks. the screen will actually have seperate power from the n64 most likely tho so i will have much more time to safely run it. so far for all of my components i need i have discovered this is gonna cost about 130$ is this realistic? do you think i can save?

I think that's pretty cheap. Remember you are probably going to break a thing or two.

Yea im perfecting a new method seeing if i can use a cheaper screen and other stuff. So far half the stuff im buying is the controller the console the drop down regulator the tact switches and wires. The rest ive got so im maybe even gonna get even more for less xD thnx for all the feedback ill post if my method ends up working well and post pics. How many people use a different screen when making a portable? Its not looking that hard.