Higher ISO level means more sensitivity to light; on a sunny day there is more available light so you don't need a high ISO film. When there is less available light (on a cloudy day for example) you'll want a more sensitve (higher ISO) film, otherwise you might have to use a wide lens aperture or a longer exposure time (with a tripod) in order to get correct exposure.
Night shots are the exception here. Assuming you don't use flash for night photography, you're going to need a particularly long exposure time. Confusingly, once you get to a certain exposure time, lower ISO films actually become more sensitive than higher ones.
As for the lens, it's not specifically designed for digital and will work fine on your camera. It's a good option, but it's a commonly available lens and they're selling it for the usual price, so don't feel the need to get that one straight away if you're still unsure.
Night shots are the exception here. Assuming you don't use flash for night photography, you're going to need a particularly long exposure time. Confusingly, once you get to a certain exposure time, lower ISO films actually become more sensitive than higher ones.
As for the lens, it's not specifically designed for digital and will work fine on your camera. It's a good option, but it's a commonly available lens and they're selling it for the usual price, so don't feel the need to get that one straight away if you're still unsure.