How hard is it and how long to change heater core in 92 astro van?

the front heater core has a very small leak in it, I am not looking for a quick fix I just want to know how long and how difficult it is to remove and intsall a new one, I can purchase the heater core for like $18.00 on ebay and I am thinking about doing this myself. thanks|||Depending on your skills, it probably takes a few to several hours to do. Best thing to do is get a repair manual like a Chilton or Haynes from a parts store (they run around 25.00) or online through Eautorepair.net---small fee---and read the procedure on doing it. If it seems like too much work, get some quotes from repair shops on doing the job.