Why don’t you take it to Honda and get it rebuilt. Getting this tranny fixed the right way would be conducive to this car maintaining its 40+ mpg etc. Or take it to a shop to get it rebuilt. If you buy it used you are going to encounter someone elses problem and what not. How many miles are on it?
Or just shell out the cash and buy this one
http://cgi.ebay.com/ebaymotors/JDM-Honda-Civic-HX-1-6-96-Auto-Transmission_W0QQcmdZViewItemQQcategoryZ33727QQihZ014QQitemZ330056435765QQrdZ1QQsspagenameZWDVW
Or convert it to 5spd and get like 45-47+ on the highway with 290K miles on the car like my gf’s dad does, car is real champ.