Hi, thank you for using Intuit ProFile Community

As long as the original return was e-filed you can refile the return. You would need to preparer the return as you want it to be reassessed by CRA. You would therefore need to preparer the complete T1 including required changes.

Hope this helps

Should I create another return altogether with the correct information, and refile

no, you would need the DCN of the original return, and even with this i am not 100%  sure it would be accepted becase EFILE ID is different.