With a very few exceptions (Laagerlander being one), you can sub any manufacturer's extract for anothers. It will not be the same, but if you have not tasted the original, you will not know the difference. ...... You will probably get more variation from the brewing process that from the difference in extract.
As Shuf said, not if it is pre-hopped or not. Replace like with like.
After you have done a few batches, I would recommend you just stick to recipes that use light/plain/pilsner/X-light extracts and specialty grains. They will have a lot fresher flavor, you will know what goes into the beer, and you will get an understanding of how the specialty grains affect the flavors.