1) No, the specialty grains, hops, and yeast really do make a big difference in both color and flavor. Always try to get the lightest color extract they have. And do a search on the boards for late extract additions, good method.
2) Wort chiller is not necessary (I never had one for extracts) for 3 gallon boils, but if you move back to AG or 5 gallon boils, you will need one. A thing to consider in the cooling is that between about 130 and pitching temp is when infections could happen, you want to minimize that time.
Also if you are doing batches back to back using the same yeast, you can pitch the second batch right on top of the yeast cake leftover from the first.
Welcome to the boards.