If your instructor is willing to teach you on it then go for it. But by all means, DO NOT try to fly this alone.

Is the PTS the ARF or RTF version?

Tower has a field starter pack for $119 that has all the required field equipment to get flying. http://www2.towerhobbies.com/cgi-bin...&I=LXL419&P=ML

Read through the first 50 or so pages of the P-51 PTS ***Trainer*** thread in the ARF/RTF section for all the necessary prep and mods.
1. Remove speed brakes (seems to be the consensus by everyone)
2. secure the antenna
3. reinforce the wing saddle area
4. Fuel proof the fire wall
5. locktite all exposed threads
6. May want to have the aileron servo mounts checked along with the landing gear area for weakness.
7. Unless you will be transporting it with the wing off, buy the charge jack for quickly charging without having to remove the wings. http://www2.towerhobbies.com/cgi-bin...&I=LXJ778&P=ML
8. Buy a exhaust deflector (RTF version) http://www2.towerhobbies.com/cgi-bin...&I=LXL378&P=ML
9. Your instructor should give the plane a complete inspection, tune the engine, and maiden the plane for you