I'd test the cooling system for exhaust gas before jumping to a blown headgasket, especially on these motors since it's just not that common. It does happen but it's not very often unless it's been overheated a bunch of times.

If it truly is a HG then I'd just yank the heads and replace the gaskets and headbolts (they are TTY bolts) and call it a day. Can be done with basic tools other than the torque angle meter needed for the headbolts. If done yourself will come in way under that $2400 mark.