You've opened a bucket of worms here. First I'm going to assume that you mean the PTS P-51, any other P-51 would be insane as a trainer. I personally don't really care for the PTS as a first plane but OK for a second plane. But you will also hear from others that say it's OK. I also believe that it has structural problems, especially in the landing gear mounts.
I would rather see you begin with a 40 or 60 size high wing trainer type and I don't mean a Cub or Decathlon either. I mean a TRAINER. Crawl before you walk for at least a day or two.

Also be sure to get the help of an instructor because there is one serious difference between a plane and the other vehicles you have. If something goes wrong, you can't just cut power and sit while you figure out what to do. If you do, WE call that a crash.