Quandary

My car developed some problems since this past Saturday and an opportunity has come up to modify it. However I'm unsure as to whether this is the right path to take since I feel there's still more to be had from the car's current setup and the driver in the equation has not been balanced with the car's potential. On the other hand it would be a colossal waste of money to repair it and then decide to modify it at a later date. Comments?