being a mechanic myself, these are the things I recommend doing while the headgasket is being done. I have done this job around 20 times so far already lol
- valve stem seals and valve job if the sealing is not very good (leak down test or visual inspection once the head is off will tell you) also replace all 16 lifters.
-Timing belt, balance shaft belt, balance shaft tensioner, timing belt tensioner bearing, timing belt hydraulic tensioner, idler bearing, camshaft seals (x2) crankshaft seal, balance shaft seal, oil pump seal, cam shaft plug (if 95-96 dsm) water pump. Valve cover gasket. Intake manifold and exhaust manifold gasket, injector seals.
Also recommend checking the cylinder head for flatness (machine flat again if not in spec, or replace head), pressure test the cooling system galleries, clean the cylinder head and blow out all oil galleries
ARP head studs and a OEM gasket (mitsu) are also recommended. Going to a MLS gasket will usually require decking/machining the block as well as the head, which will require complete disassembly of the bottom end as well. At this point, things get exspensive.
also how is your mechanic determining the head gasket is indeed blown? Best test is to check for hydrocarbons in the cooling system with a gas analyzer. (not a ton of shops have this anymore)