Shakedown is tough. You don't mention whether you're trying it acoustic or electric, or in a band or solo? Also, if you're using the Legendary Licks DVD, that is one of the best ways to learn as he slows it down. You can play the Em and G7 in the open position, but won't sound as good. I suggest either practicing the correct fingerings and chords, or working on the rhythm using open chords and when you have that down, moving toward the other chords. If you can't see what the fingerings are, use one of those "chord finder" programs, or ask at this forum for how to finger them. For Em at the third fret, you can just move a Dm fingering up two frets. Hope this helps.
"The only funeral you should ever try to interrupt is your own, and that should be a full-time job." -Kinky Friedman