General A5 Marker Help

Hi Everyone, Incase you dont want to read the wall of text the main question is - Is it safe to purchase used equipment online off of ebay? - Also, is any of the equipment i have listed below too complicated for a newbie or simply not good parts?
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So im looking to buy my first paintball gun, i have plaid paintball for years but always rented or borrowed guns from friends. Ive been looking around for a while and so far ive got the basic setup that i want down. I will mainly be using the gun for friendly games of woodsball. I was looking online and i found alot of people selling the new model of the a5 with the accessories i wanted for alot less then the website, so my question is - Is it safe to purchase used equipment online off of ebay? - Also, is any of the equipment i have listed below too complicated for a newbie or simply not good parts?

The equipment I definitely want is
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- A5 with Response Trigger, cant use HPA or NO2 with the RT
- 20 oz CO2
- 200 round cyclone hopper.
- A5 Flatline barrel with foregrip
- A helmet, not sure where to buy from.
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Also I am planning on buying some other stuff, possibly at a later date.
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- A5 flatline battleshroud for accessories
- Tippmann Fill Station/Line for filling my own CO2
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Thanks for all your help!