Hi Roy, Welcome to the forum, and congrats on your new little friend.
Does s/he have a name yet? Any idea how old he might be? For instance does he still have bars(stripes) on his forehead going down to his cere?
Heed the advice of the above posters especially about keeping him out of drafts, be they warm or cold drafts, and farther away from the kitchen would be better. They really do like to be around people, they are social creatures, so if he can be where your family hangs out, say in the living room? that would be nice.
Also the point about non stick cookware being toxic!!Another VERY important piece of advice.
Have his poops returned to normal yet? Runny poos could very well be from the stress of a new home, many go thru the same. But if it doesn't clear up soon please get him checked out by an Avian vet. Call your nearest vet and ask them where the closest AVIAN vet is located and get their number so you have it in case of emergency.
I think the frequent head scratching on a perch could be the start of a molt. Their heads get itchy and you may start to see what looks like little black spots on his head. These are the beginnings of pin feathers...new feathers.
Take it slow with the little guy/gal. Move slowly around him and talk to him lots and lots. Never try to force him on to your hand/finger. If he shies away, respect his feelings and back off. It's best to start by just letting him get used to your hand being in his cage, holding it very still maybe resting on a perch and talking to him softly.
Have fun with your new buddy. Let us know his name when ya decide on one. THAT can be a hard job. LOL
Oh and btw? About the "voice change"?
You will probably start to notice many different sounding. Happy/excited chirps... mad budgie sounds... distress call...calling to you...singing to music.. you'll pick up on them after you've had him for a while