Yes, your 2018 tax return now needs to include From 8606 to report the nondeductible traditional IRA contribution. If the original excess Roth IRA contribution was reported on 2018 Form 5329 and the penalty paid, Form 5329 will also need to be amended to explicitly show that there is now no excess contribution. [Critter's answer is wrong with respect to this.]
There is no need to wait to amend. In TurboTax you'll revisit the Traditional and Roth IRA contribution section, make sure that you have entered the Roth IRA contribution and, when TurboTax indicates that it's an excess contribution, indicate that you had the contribution ($5,500) recharacterized to a traditional IRA. TurboTax will prompt you to prepare an explanation statement that needs to be included with your amendment which should indicate the amount contributed to the Roth IRA ($5,500), the amount recharacterized ($5,500) and the earnings-adjusted amount transferred to the traditional IRA. TurboTax will prepare Form 8606 to show the nondeductible contribution.
Since your recharacterization was performed after April 15 after having timely filed your tax return you must indicate “Filed pursuant to section 301.9100-2” on your Form 1040X. You'll need to mail the Forms 1040X, 8606 and, if originally filed to show the excess Roth IRA contribution, the corrected From 5329. You'll need to prepare Form 5329 manually since TurboTax will simply remove the entries on Part IV, but you actually need to now indicate that $0 was excess to correct the originally filed Form 5329.
After amending, you can ignore the code R 2019 Form 1099-R that you'll receive next year since you will have already reported the recharacterization. If you enter it into 2019 TurboTax, TurboTax will ignore it other than to remind you that the recharacterization was reportable on your 2018 tax return. If you enter it into 2018 TurboTax, TurboTax will also ignore it.
