there's no continuous autofocus, yea, but a lot of people (myself included) use a 35mm adapter on their HVXs or other cameras, so we're used to not having continuous autofocus while we shoot. it's not really that hard at all, you just have to learn how to change focus on the fly. you can also just use a higher f-stop to get deeper depth of field; it's really easy to get deep focus with a DSLR, it's not like you'll have shallow depth of field all the time. plus learning how to change focus quickly will make you a better filmer.
the 18-55 lens isn't good. I got one with my T2i, but I bought better lenses almost right away. it's cheaply made, the aperture changes as you zoom, you can't get a super shallow depth of field, and it's not good for low light.
you will definitely need a UV filter, mainly because it protects your lens. If you get a bigger lens, like the 17-55mm f/2.8 IS or the 70-200mm f/2.8 IS, the UV filter will be fairly expensive because of the large diameter of the lens,but it's still a lot cheaper than having to buy a new lens if something hits it.
You will also want a Neutral Density (ND) filter if you'll be shooting on snow. Makes the image darker so you can have a wide aperture even if it's really bright out. I have a Tiffen .6 ND filter and I use it a lot. I would also recommend a Tiffen circular polarizer, they can cut reflections out of windows and can make the sky a really rich shade of blue.
