If your transmission is broken, sometimes replacing it, rather than repairing it, may be the better option. Instead of spending hundreds or even thousands of dollars to replace only what is broken, leaving everything else in place, you can install a 100% brand new transmission. With every component being new, the chance of something else breaking and leaving you in the same situation is greatly decreased.
If you're looking to change from an automatic to manual transmission or manual to automatic transmission, a new complete transmission can help you complete the job.