The rough shifting could be due to too much vacuum getting to the Transmission Vacuum Modulator. There is a white plastic Valve on the back of the Fuel Injection Pump that controls this.
If the vacuum is OK your problem is most likely due to wear in the Transmission.
Here is some info that will explain things in detail:
http://www.continentalimports.com/ser_ic20242.html
I was having harsh shifting from 1-2nd. When I changed my Transmission Fluid I added some Lucas Transmission Sealer and that helped a lot. But the Vacuum issue needs to be checked first.
Do it yourself links:
http://www.peachparts.com/shopforum/forumdisplay.php?f=82