Here is a good place to scope out some manifold designs and do a little more research: http://www.homemadeturbo.com/tech_projects/B_manifold/

The retention of powersteering depends on the manifold design and wastegate placement. It also will come into factor when the compressor housing is on the drivers side of the car and in that case, power steering must go.

Keeping your A/C will be pretty tricky with a DIY turbo unless you stick a tiny downpipe on the kit. Anything approaching "true" 2.5" will interfere with the A/C compressor, so it will have to be taken out. By true, I mean circular, not oval like with the Greddy turbo kits.