How old is the unit? Most evap. coil leaks can't reliably be repaired. Repair one leak , a month later , another , next month , another . You get the picture. It's in your favor to bite the bullet, and install a new unit.
Depending on the age and condition of the air handler - If unit is under 5 years old the part should be under warranty from the manufacturer, and you would probably just have to pay for the installation of the part. If the unit is over 5 years old you need someone to look at the overall condition of the air handler and determine if it is worth paying for a new coil + installation. In SW Florida the avaerage life of an air handler is around 8-10 years, due the the harsh conditions our systems have to deal with. We have 2880 cooling hours ( highest in the country) and extreme humidity. These conditions really take a toll on our systems. Either way unless it is a minor leak,that is easily accessable it is usually not practical to try a repair.