In some cases, and if your blown head gasket isn't too far gone, you can eschew the need to replace it. A typical replacement to solve Subaru head gasket problems can easily cost upwards of $1,000. However, if you catch on to a blown head gasket early on, you could instead use head gasket sealants. You can typically find these for under $50, and they mostly work rather well. Although, do understand that these solutions only work if you apply them early on, as a head gasket that's too blown will require a replacement, regardless. All you need to do is pour some head gasket sealer into your radiator. Give it a few to circulate around the engine, and its chemicals will slowly re-seal and re-condition the head gaskets.