Diamond screen not working

[nyclegend20]

my brother has the htc diamond for sprint and the screen just stopped working all of a sudden
it was not dropped no water damage
screen is perfect condition not even a scratch
it has mighty rom on it, so can i still take it into the sprint store for repair or will the void it cause of mightyrom?

how can i put stock rom back on the phone without using the screen?

it has a lock on it which i cant unlock with putting the code into the phone