With the nexus 5 i believe if was only purchased from tmobile. If you swapped i don't think it is a problem because its in sprints system already. Just buy it from sprint or Google play to be safe.
I hope there's a new radio. 3g drops constantly. But comes back in a second. This phone has been at lg three times. They finally said its software releated.
New google play don't know the whole version but its 5. Something. Here's the apk. http://www.apkmirror.com/apk/google-inc/google-play-store/google-play-store-5-0-31-apk/