I have a doc intended for print but when I export CMYK the copy which is meant to be a neon colour appears dull.
Some of the people in the image appear normal, but one person appears orange. When i export RGB the orange character appears normal but the copy is still dull.
What should i do to make the copy appear vibrant and the images all appear normal?
Neon is out of gamut for CMYK and will require an additional Spot color plate (and output on a printing press). You might want to reconsider that choice if cost is a consideration.
Your color shift problem on the photo is going to require more info, and maybe some screen shots, I think.
Not the answer you want maybe, but: learn about Colour Management, Gamuts and color spaces first to understand what is happening. Neon is out of gamut for CMYK and your RGB images can change in CMYK spaces....