I went to look at a track bike today 848 evo all seems pretty much okay apart from the speedo isn't working properly as it is not showing the full display, if I get a new speedo is it as simple as unplugging the old and plugging in the new second-hand one?
No, you need the code card to program the keys into a new dash and need the programmed keys if you buy a second hand one.
The dash is coded to the original card. The only person I know who can help with second hand dashes is in OZ Riderlogic home page