Ok my front u joint went and im looking at a rebuilt driveshaft for $150 or a new one for $210. the question I have is that the existing one and the rebuilt one have like a little cover on the end with something resembling fan blades. Do I need to have this because the new one doesnt have it. Heres acouple of pics.

 

mine has that shield looking thing your talking about, in all 5 rx-7's around here, but it doesn't look direly important. i'd go with the rebuilt one if it has some type of warranty and replaceable u-joints.

 

you dont NEED it but its a dust shield and has some kind of cooling properties.
i have one on mine but i think if my driveline went out and i get a new one that would not be a requirement. i only drive in the city