I was wiped out financially during the dot com bust. My 401k was all in company stock that went from a peak value of over 800K to zero. I am 46 years old and now have gotten back on my feet, but still behind the retirement investment power curve. I recently changed jobs and have 50k to roll-over to either an IRA or an employer 401k. I am currently contributing to my new employer 401k but need some feedback concerning investment options of the roll-over from my previous company. I am leaning toward a roll-over to an IRA and diversifying it myself. My questions are as follows:

1. Roll-over to an IRA or to new company's 401k (current investment returned 17% last year).
2. If I roll to an IRA, given that I am 46 years old, what would be the best way to diversify it given I plan to retire in 20 years.
3. I currently utilize TD Ameritrade as my discount broker. Any recommendations for alternatives?

I am no investment pro by a long shot. I do need to take on some additional risk to catch up. Any feedback would be much appreciated.