Your engine is similar to some of ours.
V6 DOHC per bank (Quad cam)
First up, how many miles, good service history etc, needs to taken into account.
If it had say 300000 miles, I wouldn't even lift the hood, I would quote for an engine straight up.
It then needs to be proved if it has a head gasket issue.
Some simple testing and observation will reveal that.
If you are low miles under 120000, and good service history, and it is only one head gasket (since you have 2 being a V6), a very rough guess would be in the $2000-$3000 range.
A lot of dismantling needs to take place to do a job like this.
I would sooner replace the engine with a good second hand engine from a wrecker.
Some wreckers will do the job for you.
A whole engine swap could be around the same price or a little more dear, but in the end a better result happens.