Prince Red is a higher end recreational model, so there is no doubt that you have acquired a decent racket for your level. The O3 Red is an older version as opposed to the EXO Red. I would guess that the strings are a few years old.
If you are 3.0 and can rally consistently, using the sweet spot of your racket, then by all means a new fresh string will increase the feel of your ball contacts.
But if you are a 3.0 and still lack consistent, sweetspot hitting, and you are framing or using the outside of the sweetspot a lot, then save the money and keep the old strings. It probably will not improve your game.
To my knowledge, the high end rackets that come with factory strings are pretty good, such as the Prince Premiere. If it is just regular "synthetic" and you are a decent player who is already familiar with personal favorite strings, then new strings are always welcome. New strings always feel better... (as longs as you are hitting the sweetspot consistently)