Why don't you have a tune? Car come that way from the previous owner?
Tunes can vary. If you pick up a Cobb Accessport, it can be anywhere from $300 to $600 if you buy vs. used. This is a general off the shelf option that is generally utilized for *any* car similar to yours for stage 1 and stage 2 (and protuning possibilities).
Protune at a tuning shop on a dyno can run anywhere from $300-600 for that session and is the best option for your specific car, specific mods, and environment.
E-tune would require the use of a Tactrix cable and a laptop. A tuner sends you a map...you load it onto your ECU yourself, and run logs. Send logs back to the tuner, and he makes adjustments. Rinse and repeat until you have a good tune for your car. Also better than the accessport since it is more specific to your car and parts.
Generally you can expect 30-50whp over stock depending on dyno, environment, specific parts, and the type of tune.