You say if you don't hear from him in 9 days you would open a case. . . . What kind?
It has only been one day, or just over 24 hours. In that time you have sent 3 messages to the seller. Yes, he understands what you want.
He gave you a rough estimate for the shipping cost, but after you win he must package it up, weigh it, and get an exact price for you. Granted, he could have had it ready to go so as to quickly get the cost no matter where he was to send it, but perhaps he became distracted by something else in life. Near as I can see, he only has one other item listed, and he put up the listing shortly after you won your guitar yesterday.
Anyway, you'll be pleased to know that he cannot "cancel it on you". To cancel a sale, a seller must send the buyer a Request for Cancellation, whereby the buyer agrees to accept thus ending the transaction. It's a Mutual Cancellation. He knows you would never agree. So if he does nothing he'll have to pay fees on the total amount of the sale.
Some people are better than others at getting things done quickly. Speed and attentiveness may not be his strengths. If, after several more days you have not received an invoice and the ebay Pay Now continues to show no shipping fee (with the resultant inability to pay), you could always give him a call.
To get his phone number, up on the right side of the Search bar you will see the word Advanced. Click it, scroll down the left side to Find contact information, and enter the info on the next page. You will get his contact info and he'll get a note that you have requested it, - which will surely come as no surprise.
For now, though, I'd say give it a few more days. One day is really too soon to be getting worried.
When he does finally get the shipping fee on the invoice, you might like to send him a note of thanks explaining that your excessive glee at winning your guitar rendered you deliriously over-eager to pay instantly . . . the sooner to get your enthusiastic hands on it.
Otherwise, if a seller were to ignore you after a sale and not send an invoice, there is not much you can do. Well, you could leave feedback. You've got 60 days in which to do that.
On the other hand, if you have paid for an item and it does not arrive or is not as described when you get it, you have 45 days in which to file a claim. The following link will tell you all you need to know about that:
http://pages.ebay.ca/help/buy/item-not-received.html
Best wishes for your new arrival. ♪♫• 
