i have an 09 legacy wagon 2.5 automatic PZEV. The head gasket is gone and since it has 433,000 km, about 270,000 miles, I am thinking about another engine with fewer miles for about the same price as a head gasket replacement.

 So, the question is; can I just get any other engine for that year, assuming auto trans or will too many manifolds and other parts have to be changed too and make it a very complicated and expensive job ?  

it switched up fine and runs beautifully. Thanks for all the input from such a friendly forum.

Glad it worked out. What engine did you end up using? Did you have a shop swap it out? If you have further such related questions maybe try the new gen forum, that gets a lot more traffic than the subaru transplants forum.