Hello and Thank you for choosing Just Answer.
Depending on what exactly is wrong with the transmission and what you would want to do either have it rebuilt or have a new transmission installed. A rebuild will run approx. $1700-2200 and then a new transmission will run $2200-2500 but will come with a 3 year or 100,000 mile warranty. It does sound like it is an internal problem and looking at the mileage, a new transmission would probably be best.