Circuit Board replacement from an old phone, what could the side effects be?

hey,
I have a blackberry z10 which is almost 1.5 years old . Apparently a local mobile service center has made the phone dead while replacing the display. after 3 months of tiresome legal fight against them , they have manged to reach a solution to replace the existing circuit board with that of an old z10 . I'm Not sure about the after effects , But What about the genuine blackberry parts and the imei number ?? and the side effects ?? any previous experiences ???
HELP .....URGENT .......

Assuming that the mainboard would come from a different phone, then the PIN, IMEI and serial number would be that of the different phone, not your original phone.

Of course, if this service center was stupid enough to break the mainboard in the first place, would you trust them to try it again?