I just finished a heater core in a 1998 F150 4.6 liter and it wasn't as bad as everyone made it out to be. I started it yesterday and in a couple hours had the old core out. The blend door was also broken so I had to wait till today to pick one up from Ford (along with the new clips and O-Rings for the heater lines). I put it all back together today in about 3 hours. All in all not too bad of a job. I think any do it yourselfer should be able to handle it. This was for my neighbor and he was quoted $700 plus parts from a local shop. OUCH!