2007 Saturn Ion - Check Engine & Coolant Lights on & A/T shifting very hard

My husband replaced #10 fuse on engine compartment fuse box and this solves the problem temporarily but after driving the car about 10 miles the fuse blows again which sets on the Coolant and Check Engine lights and transmission shifting very hard.

Hooked computer up to the car to find what codes come up:

P0030 – H02S – Heater Control Circuit - Bank 1 Sensor 1
P0036 – H02S - Heater Control Circuit - Bank 1 Sensor 2
P0053 – H02S - Heater Resistance Bank 1 Sensor 1
P0054 – H02S – Heater Resistance Bank 1 Sensor 2
P0102 - Mass/Volume Air Flow Circuit – Low input

Took car to mechanic who replaced 2 oxygen sensors and 1 heater solenoid, mechanic said the lights went off and on test drive car was no longer shifting hard.
We drove car home and drove about 30 miles total before all problems came back.
Mechanic said he checked as much electrical wiring as possible and saw no problems. Paid $200 for above work.

My husband keeps replacing the fuse and he knows something keeps causing it to blow. He thinks some wire somewhere is not grounded causing fuse to blow but that is not what the codes say.

Here are suggested possible solutions from mechanic on line: Possible Causes
The following are malfunctions that could cause a rich condition.
• Fuel pressure too high. Perform pressure leak test
• Leaking fuel injector(s). – Perform pressure leak down test
• Vacuum leak around the MAP sensor grommet.
• Oxygen sensor contamination
• Restricted exhaust or air intake
• Fuel Vapor Canister saturated with fuel

IMPORTANT: If the front oxygen reading voltage is above 600mV and the rear H02S is above 600 mV all the tie, the 02 sensors are probably not at fault.
What do you think? How can I find a mechnic that specializes in this kind of problem?