350D has a sensor of APS-C size. which is smaller than a full-frame (35mm film frame size) sensor. That is why it is affectioned known as "cropped sensor" since most of us refer to most focal lengths in 35mm equivalent.
17-85 is not L lens. anyway for a body like 350d, not very worth to get L lens i think. the weather sealing is not beneficial to you since your body doesnt have it anyway. you will be better off getting 17-55 f2.8. its not an L but it has very good IQ. 70-200 f4L is also worth considering for a telephoto. btw its "lens" for the singular form not "len". "lenses" would be the plural form.