Hopefully as a folder, it doesn't need much assembly.
Unfold, straighten the bars (very complex task requiring an aerospace engineering degree), then ride.
Oh, it never hurts to double check the derailleur adjustment. Perhaps a LBS could help you with derailleur adjustment if you aren't ready to take the plunge.
I never would return an E-Bay purchase because I decided that I want something different. Only if there is some issue that wasn't in the ad. You can always try it out then resell it on Craigslist if it doesn't work out.
That does look like a moderately small frame. How tall are you? A "unisex adult"?
Anyway, put it together, ride it, and decide if you like it.