My PHD advised me stop Effexor and start Lexapro. From all that I have read, one is supposed to wean off Effexor. He made no mention of all the pitfalls that I have read about when one stops Effexor. Will Lexapro compensate for the Effexor change? Concerned!!!

I'd be slightly concerned too. Lexapro is an SSRI while Effexor is an SNRI. It would ok (usually) if they were both SSRIs or SNRIs.
When I switched from Effexor to Lexapro I weaned off Effexor first. You might want to call your doc and clarify or ask your pharmacist if it would be better to wean off Effexor.