I have the plastics sanded the next step is a sealer then a layer of black then a layer of a flip flop paint then a layer of clearcoat

I will be using a gravity fed paint gun.
I was going to pay someone to do this but how hard would it be to do it myself?

new paint ready

all parts primed and sanded

I painted this black cherry. I was not worried about the scratches in the metal. so ignore the divits and dips as i did not fill these

That depends who you are..
We don't know your ability.

If you have an amount of painting experience and knowledge, it will be easy.
If you are a first timer, you'll probably be disappointed with the outcome, but be one step closer to becoming an expert.

Have done heaps of plastics, I usually scuff with grey scotchbrite pad, wax and grease remover, adhesion promoter, (plastic primer), high build primer, sand till smooth, base coat, then clear coat, seems to hold up well until you crash into a tree make sure you scuff it real good, even go with a 1200 grit wet and dry first to make sure all the oils are out of the plastics, I ride KTM's so everything is KTM orange basically just orange tint straight from the tin.. (single stage) Sometimes I will use a metallic for frames and for a bit more bling. If there are any nicks or deep scratches you want to fill make sure you use a plastic filler not standard bondo. I was going to try adding a flex additive into the paint but haven;t yet.

Cheers
Chris.