Hi rkd,
"Can anyone tell me does a patent apply even if you are only making changes to another person's product as he has above!? "
Yes it is possible to file a patent for "improvements" to an existing device, but it must be novel in some way, and not an obvious "next step" to someone "skilled in the art".
The fact that he got the original manufacturer to make the improvements, may mean that they would have some ownership of the intellectual property (if there is any in this case-due to disclosure-see below).
The device is on the market, so that means that is now considered prior art, as it has been disclosed, so it would not be possible to patent in Europe, but there may still be a possibility in the US, as thay allow a period of 1 year after disclosure in which to file a patent.
Your friend would be well advised to visit a patent attorney, as the area is complex.
Good luck