There are many things to consider other than a Key which you have used earlier with the account.
Of course, Keystore and the Key used to sign for the previous version is the most relevant entity you must have for updating the app.
As per the Google standards you should mention all the notable changes made to the app in the playstore console (This is mainly for the existing users to consider the app-update). You should be increasing the versionCode in your app (build.gradle) from the previous version to update your apk.
There may be some additional surveys / questions introduced by Google in order to attain certificate/rating to your new app if you are using playstore after a very long time.
There are different levels of update options available in playstore console (manual release, region wise release, partial release. etc) make complete use of everything. Good luck.