I mailed my 2017 return Dec 22, 2018 and cannot get my refund Status from Where's My Refund tool? How do I get the status?

It might be awhile before you see anything -- you mailed it around the time a government shutdown began.  It usually takes about four weeks before you can see the status of a mailed return on WMR.  Give it some time--the IRS just re-opened.

And now to file a 2018 return you need to use 0 for the 2017 AGI since you filed 2017 late.  So if Turbo Tax transfers your 2017 AGI into 2018 you will need to change it to zero.