you'll have to contact Vanguard and tell them you want a return of excess contribution and the earnings on it. They'll tell you what form to submit.
This contribution will not affect your 2018 taxes as it has been done in 2019.
Vanguard breaks out the contributions by year... the website says I have no more to contribute for 2018 ans $7000 to contribute for 2019... does the IRS get notified what year a contribution is for?
You will be sent IRA information from Vanguard to enter for your taxes each year. Please see the IRS website regarding IRA contributions - <a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/retirement-plans-faqs-regarding-iras-contributions">https://www.irs.gov/retirement-plans/retirement-plans-faqs-regarding-iras-contributions</a>.