Yes, it is recommended to wait to have the original return processed but if you needed to you can send the amended tax return (1040x) in earlier. Generally, you have 3 years from the date you filed your return (or 2 years after you paid the tax due, whichever is later) to file an amended return, which means you don't have to get it done by the April 15 filing deadline.
Once the 1040X form is released you can amend your tax return and see how the added W-2 changes your return, if you get an additional refund then you have plenty of time, even after the April 15th. If you owe taxes back then it is recommended to pay them by April 15 to avoid incurring any interest. You will have to print and mail the form 1040X.
Please, keep checking the following information on how to
amend your return; it will be updated once the 2018 form is released:
https://ttlc.intuit.com/replies/3288565
