Actually, performance upgrades, if done correctly, do add value to the car, just not as much as they originally cost. Look at it this way, if you put a few gold bars in the back seat would you still sell the car for the same price as without them? I have converted a civic to manual before. It can be done, yes, but it is a bit more work and requires buying a special mount, doing special wiring, making a custom sheet metal piece to fill in the shifter hole, changing ecu, linkage, clutch pedal and lines, etc etc etc.