Richard, your mech needs to pinpoint the sound before cracking it open, if at all possible. With a stethoscope, it's much easier to do this.
If the sound is coming from the top end, feel the cam covers (bulged area), if you can "feel" the tick, it's chain slap & the tensioners / cam chains need to be addressed.
If it's in the pan only (& not so much the trans case), it's possibly bearings.
If it's in the front / dampener area, could be a broken / worn woodruff key.
If it's engine-front, could be a failed timing belt tensioner / belt slap.
If it's in the oil pan & trans case, could be throw-out bearing / clutch-related (for 5-speed).
If it's in the exhaust Y-Pipe / cats, you could have a broken-up catalyst brick or an exhaust leak.
Check compression, make sure you haven't blown a HG cylinder-to-air too.
As you can see there are just too many things to throw time & money at without nailing down a target first. If your mech does dive into a certain area, negotiate for other items to be addressed at the same time to save labor - example, if you tear apart the timing covers & dive into the tensioner, think about timing belt, front crank seal, crank sensor, water pump, etc.
Good luck!