This whole project begs the question, why do this?
1) because you are interested in figuring out how to control this LCD because you think it might be fun.
Might be worthwhile
2) you bought it on ebay really cheap and were hoping to use it in your application.
Not worth the effort, unless you don't care and are really doing this for 1.
3) you like to waste time reverse engineering someone else's product so you can clone it.
This might be worthwhile, but also gets into a grey area of legality.
As you have no datasheet nor any user guide, you will have to capture all the data, not on a scope but all the data for all possible transfers to the LCD using something like a logic analyzer. Then you have to start trying to determine the protocol from all that data, by trying to see if you can figure out what part of the serial data is address and data. Then you will have to determine which bits affect what parts of the LCD screen based on the numerous transfers you've captured.
I expect this may take weeks of work to figure all this out and then you will likely still end up with some mysterious transfers that magically make it work/not_work.