When I did my 91 Previa I had the local toyota dealer give me a quote for Replacing the bushings as if it was 94+ Previa as toyota makes a bushing kit for the later Previas and therfore has a flat rate for the job. The labor is the same, just the bushings are not available from Toyota for the earllier Previas. I got my bushings from ABC Mart on Ebay. The Toyota mechanic said they fit perfectly. I doubt that you need a whole new drive shaft. The problem is usually the bushings. I think I was charged 4 hours labor. I felt it was worth it some others on this forum thought it was excessive. I did not feel like messing with the job in an parking lot for an apartment complex.
Below is a link to my original post. The key point is that after market bushing kit is available for the earllier previas. Toyota only makes a bushing kit for the 94+ previas.