I'm so glad you took my advice, sure you will NOT be disappointed with a Yamaha over a Korg, well, for what and how you want to use it. I do happen to like both, for very different reasons of course.
Yes, with your condition and the fact your really woodwind/guitar bias, then the 900 with looper really will suit your needs + there are other extras you might use including greater memory on the 900.
As others have pointed out there is a whole host of info. tutorials and files you can get from here, so you should be fine.
There are lots of people here with FAR MORE skill and knowledge than myself, as i am very 'load and play' and am very lazy with regard to what these things are really capable of, ( I only skim the surface...lol ) but if I can help in anyway, then do get in touch.
Notice with the MFD files that a registration bank is automatically created for every playlist entry that is listed for each song ( registrations are needed to 'drive' a playlist entry ) These banks have 7 of the 8 buttons empty are handy to edit and resave the song for different verses, endings etc. using these empty slots.
Yes, some of the style and voice substitutions are not great ( even using the UK Tyros 5 MFD files ) so it is good to be able to re-save with perhaps other styles and voices of your own choice, but I do find these files a great base to work from as a stating point.
Best regards and enjoy your new Yamaha - Keith