You didn't tell me your age or whether or not you have acne.  But unless you have very tough, oily skin, I wouldn't recommend that combination to start out with.  Why don't you try the Retin A first for a week or two and make sure you tolerate it well.  If you're fine after 2 weeks, try adding the glycolic in the morning.  If you don't get irritated, it may be okay to continue.  Please call your doctor if you have questions.  Remember that with acne it takes 8-10 weeks to see real results after a change in products.

 It depends a little on what you're goals are.  If you're using this regimen to treat acne, it seems reasonable although there are many other possible options too.  If you're using this as an antiaging regimen, I can think of better combinations.  Dr. I