Steve looks like a very pretty boy. How long have you had him? I'm glad you're getting him a companion. Since she's a girl, you'll want to get Steve neutered.
Is there a reason you're not doing the thirty-day quarantine, in separate rooms? I'm asking because some conditions, the parasite giardia in particular, can take as long as thirty days to manifest. (Giardia can be contracted very easily, and is highly contagious.
http://www.cdc.gov/ncidod/dpd/parasites/Giardiasis/factsht_giardia.htm
.) If your new girl is carrying that parasite, you'd end up having two gliders to treat instead of just one. Also, by following the quarantine, you'll allow both gliders time to adjust to their new surroundings and to become familiar with you, before putting them through the stress of introductions. I highly recommend the quarantine period. It's hard to be patient through it, I know! But it's very important.