Once you get your appointment, get ready for a barrage of emails, texts, and automated phone calls asking to confirm the appointment and to remember to finalize all your documents/funding. The same barrage came after my first appointment last month. Last month, I had a delivery option. This month, the only option is a pick-up. I'm only 5 miles from the nearest Tesla center.
As far as finalizing your payment, they prefer to pay via Plaid. I found that more convenient than getting certified funds. If you're waiting for funding from a financial institution, ask your lender to send you a photo of the check along with tracking (FedEx) numbers. Tesla will take that as proof that your ducats are on the way.