Paul-
Running doubles is fine.
http://fastrunningblog.com/forum/index.php/topic,228.0.html That being said, I would suggest a mix- some days do doubles, some days do singles. Also, you don't have to be a slave to exactly 10 miles a day. The big thing is consistency. Running 8 miles one day, 12 the next, then 10, then an easy day of 6 is fine. If you do the exact thing everyday, it might get monotonous (see Pete Pfitzinger's book "Advanced Marathoning" for more on this).
As for pace- like Sasha says, run easy enough that you are recovered (or mostly recovered) by the next day. Don't worry about exact pace, you can just run by feel. I'm sure you'll run faster some days and slower on others.
Hope this helps.