If you can do the work yourself, it won't be too bad, as long as you have an open space to work, even if outside.
Rent or make an engine lift. You will need an engine stand to work comfortably.
You can machine the heads yourself.
Work on calm days and if necessary work inside a tent.
Challenging, but it can be done, as long as you have space.
FMS here:https://sl-i.net/FORUM/showthread.php?18087-Subaru-Factory-Service-Manuals-(FSM)-Every-Model-USDM-EU
O.