Can i give you a piece of advice, you said in your question that the mechanic said have it checked out. That means you should have a professional look a the trans. That does not necessarily mean that you have a problem. I have seen several times on that model, broken wires on certain sensors that the only thing it takes to find the problem is a little bit of troubleshooting. Before you think about going through all the trouble of swapping to a 5 speed, at least find out what is wrong with the trans.If you decide to swap it over it is a whole lot easier to go from an auto to a 5speed than vice/versaThe biggest thing is eliminating the extra wires and you will prob have to change the pcmHope this helps!