If it uses dot 4 you can only use that but if it uses dot 3 you can use dot 4 as well.
Brake problems are pretty easy really not much to them at all, if you have an old master cylinder only do half pumps of the pedal takes a bit longer but because the piston wouldn't have traveled all the way being old it's not good to pump the pedal all the way to the floor, if you're still getting problems just get a new master cylinder not expensive for the piece of mind you get knowing you now have a new one, just bench bleed it before putting it in and be done with it.
And if you don't know what to do or don't understand something fully go take it somewhere to get it done, don't just try and then find out that you got it wrong when you run up someones ass or try to emergency stop from hitting someone and hurt or kill them, not saying you don't understand but some people don't and then find out at the worst time. It's people like that who should make you need a license to buy car parts, haha.