I have not used P90X, but I work with several men and women that have had very good results with it. I have had good results with a book by Phil Campbell called "Ready, Set, Go fitness" <
http://www.readysetgofitness.com/>
I also recommend googling the term "tabata" for a type of interval training that really works for me.
Finally, make sure and get a really extensive set of blood work done. You want to get your growth hormone and testosterone counts in a decent range, or it will be really hard to see results from your exercise.
I am 51 and have lost over 35 lbs in the last 16 months using exercise and good diet. It has definitely improved my sexual performance. It's possible to get back in shape, but it isn't easy. My goal is to get in such good shape that the providers don't ask me to pay anymore.