It depends on the option you select in the private chat. If you select option 1, improve game, stats like determination will be effected. But if you pick option 2, off field tutoring, it will effect his personality and media handling.
Personally i would. According to the website thats posted below, a player with an ambitious personality, is just ambitious but lacks loyalty, which will most likely end up with the player wanting to move to a bigger club and stuff. Whereas resolute means that the player has good professionalism and determination.
The fact that you mentioned that the player is also outspoken is a bad trait to have because that means he is controversial so could cause trouble.
My opinion is i would change his personality 100%.