I suggest using PyART.
But, for Matlab:
If you have a cfradial type data file the data are stored in 2-D arrays (gates x rays or range x time). For RHIs you need to parse through this to get the constant azimuth section to find the RHI in your volume. If you're trying to create an RHI from PPI scans, you'll need to match rays with the same elevation. Then you need to turn along beam range into along the ground range. You need to compute the height above the geoid the beam is. etc... It's a non-trivial exercise to do this from scratch and do it right. Hence, PyART.
Anyway, paring down the data you want to view is the hard part. Once you do that you can use surf.