I have to get my hamster from Petco..... please help!?

I know that they usually aren't very healthy but the only other place I can get one is at Petsmart and neither is very good. I also can't find any breeders near my area. :( When I go to Petco is there anything I can do to make sure that it is healthy? And also the Petco near me is still 20 minutes away but that doesn't matter. I've been in it several times and it looks clean and I saw two dwarf hamsters that looked pretty good. One was asleep in the corner and the other was running on the wheel. I gave a lot of information but I am going to be a first time hamster owner so I want him to live a long time. Please help me! And if you have any experience from buying at the Petco in Port Chester, NY that's where it is.