Just bought a 2005 2.5i legacy on ebay. What should I inspect!

Its a wagon with 121,000 miles. What should I look at. What should I inspect. What should I ask.

What ar ethe common problems on these things?

I know head gaskets and auto transmissions where a popular problem on the older ones.

Any help is great.

Also where should I buy a hitch at. I see I can get them with all the wires on ebay shipped for under 200.

Any advice on different hitch brands?