C14 Seat -
Corbin 2-piece - Comfy for most but pricey.
Sargent - There seem to be a lot of used ones for sale, so may not be great.
Laam - Most people seem to love theirs.
Russell Day-Long - I love the one on my C10. THE most comfy seat, but bring plenty of wallet.
Phone mount -
I use a RAM ball mount that replaces the clamp that holds the clutch lever to the bars.
Attached to that I have a Carpuride W702.
Others use an extension to the bars or else RAM ball mounts that fit in the steering stem hole.
Still others use a bracket that bolts to the bars or to the bar risers.
Plenty of mount options out there.
Make sure that you fit a vibration isolator of some kind. The QuadLock seems to be the popular choice for that.
For a paper service manual, check eBay regularly.
Personally I use the PDF version.
If I need it next to me, I have it on an old Tablet in the garage as well as on my Garage PC.