Course you can!
Just remember the mantra, long run, tempo run and speedwork, mix in a few easy runs and it will all come together.
Oh, and my number one tip, join a club, apart from the social side all the available experience, help and support will make it all easier.
At 38 my half marathon time was about 1:42, now I'm 44 I've had a 1:30 half and a 2:26 20 miler.
Enjoy.