The most cost-effective solution is to sell your car and buy an SSEi.
Second most cost-effective is to swap the entire drivetrain. Engine, trans, axles, PCM, and wiring harness. You'll still have the soft ride suspension and lack the other SSEi features.
Third would be to try to convert just the top end, including a bunch of brackets, parts, and a custom PCM tune. Your trans will not last. This option is the most expensive becaus the trans will not hold the power.
If you don't have at LEAST a 2k budget, don't consider any of these options.