no need to replace headbolts. that is dependent on the type of materials used in constructing the head bolt - Subaru's have always been reusable type.
yes the heads and valves are the same.
you can swap valves if you trust your heads more and don't mind compressing valve springs - but it's really annoying and time consuming. swapping a known good head is well worth it.
the heads don't need tested, they'll need resurfaced. you can even do that yourself, it's really easy and saves gobs of time, well worth it to source the one part needed:
DIY Head Resurfacing... or "Post-apocalyptic machine shop techniques!" - Old Gen.: 80's GL/DL/XT/Loyales... - Ultimate Subaru Message Board
head gasket kits are usually priced too high. all you need is head gaskets and intake manifold gaskets.
valve cover and exhaust manifolds are nice though exhaust manifolds are often reusable and both are easily replaced later as needed.
i'd do the timing belt kit while it's all apart. and cam and crank seals, reseal the oil pump (tigthen the backing plate screws). cam/crank seals may come with the kit if you go that route.
if it has a plastic rear separator, buy the upgraded metal one and appropriate screws. t he plastic ones can crack.
