I was sent a revised 2014 T4. What do I do? Do I need to do my 2014 taxes again?

No you do not re do your your taxes here is what you need to do.

You can make changes (amendments) to your current tax return, as well as a tax return for any of the previous 10 tax years, whether you filed by mail or electronically using NETFILE. Here’s how you should proceed to make changes:

1. Wait until you receive your notice of assessment from the Canada Revenue Agency (CRA).
2. Once you’ve received your notice of assessment, visit the page How to change your return 
3. http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/chngrtrn-eng.html?locale=en-ca&view=GBD_TURBOTAX?loca...on the CRA website.
4. Follow the instructions on the CRA website. You can change your return online or by mail.
   If you choose to amend your return(s) online, the processing time is approximately 2 weeks.
   If you choose to amend your return(s) by mail, the processing time is approximately 8 weeks.