There is really no way to know for certain which aircraft you will have. Having the tail number, using the mobile site and fleet website will give you a good idea, but I've had the a/c change on the day of many times.

Using the old adage, prepare for the worst and hope for the best should make it a more enjoyable experience for you.

Most of the 900s have DTV and power, so your chances of getting one with are greater than not. Hopefully by this time next year the 900s will be more like the 800s and 700s now, where you can almost be certain you'll have power and DTV.