Renewal is designed to be a one-step recovery: after your payment is confirmed, open your client and refresh the subscription (long-press the subscription entry and choose Update in Shadowrocket; hit the refresh icon under Profiles in Clash-family clients). Your nodes return with current details — nothing to reinstall, nothing to reconfigure.
If it’s been a long time since expiry, fetch the current subscription link from your account page first, since the address shown there is always the authoritative one. Your account, order history, and settings are kept through expiry, so there’s no such thing as “losing your account” by lapsing.
Expiry reminders go to your registered email ahead of time; renew whenever suits you and the new period extends from the expiry date.