Thanks for the comments everyone.
As an update, I took the lil' guy in for a vet exam today. He's got a clean bill of health, and we trimmed up his beak & nails too.
The best part of the story is that the vet knows the breeder ( based off his leg band ) and gave me her website. As it turns out, my lil' birdie comes from the same breeder as the young one my dad fell in love with.
We did remove the band for safety reasons, though.
I'm not at all worried about him getting the other bird. My girlfriend & him have gone back to the store a few times since then, and he won't even play with the lil' guy. ( he's still there...last one left....and sooo sweet. ) He doesn't want to get attached.
Plus, he'd need my help getting the cage both lifted and put into my truck. He wouldnt' spend that much on him, though....
Also, the store owner knows the whole story.
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So far, he's not eating pellet...and he doesn't seem to mind the other birds. He's very sweet, plays rough with me but also loves neck rubs. He lets me spray him with a water bottle if I hold him upside down.