unless your flywheel is cracked or severely warped, keep it. even if it is cracked or warped take it to a machine shop and have them see if it can be shaved down to be good again.
take it to a local machine shop, and have them shave 5-7lbs off of it. thats basicly what the "lightened flywheels" most places sell are. unless its a alloy flywheel, but those are way more of a racing upgrade and starting off can be a major pain. you end up dropping the clutch @ 3k just to get going.
its enuff to notice a difference but not so much as to kill the off the line performance.