I over filled the transmission fluid by about a.

Too much fluid can cause the fluid to foam up in the transmission causing a lack of lubrication to several parts. I don't know how much extra transmission fluid 1/2 inch is equal to. So look at the dipstick and measure the distance from the ADD mark to the FULL mark (this distance equals one quart of transmission fluid). If the distance is 1/2 iinch, then 1/2 inch equals 1 qt. If it is 1 inch, then 1/2 inch equal 1/2 qt; an so on.
If your transmission is over filled by 1/2 quart you will be ok. More than that I would buy a siphoning hose from Harbor Freight and take some of the fluid out.

Please let me know what you determine 1/2 inch equals in qts. Also Please post what you decided to do about this problem. Feel free to ask for more assistance if needed.