First off, it is very possible to ride and run. You just have to figure out the balance. Secondly, riding at a lower heartrate over long distances gives you a very good base for doing long runs and helps to prevent injury through cross training.
I also agree with Anakiwa - plans are guides and nothing more. I would figure out what the essential, core running workouts are and work around those. Don't do any tempo work until you feel like you've got a decent base. If you haven't been running much that could take a couple of months. Work your bike rides in around your runs and do your long ride after your long run and try to cluster them together. Eg Long run on Sat, long ride Sunday. You'll be a little slower on the bike but it's a lot easier that way. Take the next day off. Then try to cluster some workouts during the week.
Eg:
Monday - Rest/Yoga
Tues - Run, shorter length, harder intensity. 30 min recovery ride if you want (sometimes helps the legs get rid of lactic acid)
Wed - Low intensity ride for fun 1 hour or so.
Thurs - light run, distance depends on how you feel but I would focus on form rather than intesity
Fri - Rest
Sat - Long run, low intensity
Sun - Long ride, low intensity
I would do something like this for 3 weeks then take one week to rest where you do about have the volume on any one workout and drop one ride and run.
Repeat, adding a mile per week on your main weeks as Anakiwa suggested and viola, you're there in no time.
Living life like there's no tomorrow.
http://gorgebikefitter.com/
2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS