2002 Nissan Altima Engine mount, valve cover gasket, head gasket

2002 Nissan Altima 4 cyl Automatic 89,500 miles
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My problem is so complex, ongoing and frustrating (to me), I'll give an overview of my problem in bullets.

Symptoms before initial diagnosis
- Rough idle
- Rough gear change
- Loud noise from engine area
- Engine overheating (frequent temperature guage fluctuation)
- Rapid loss of coolant

Initial Diagnosis
- Valve cover gasket problem
- Engine mount broken
- Complete fuel system cleaning needed

Repair costs: $600

Symptoms after initial diagnosis and repairs
- Engine overheating (frequent temperature guage fluctuation)
- Rapid loss of coolant
- Lots of white smoke (never had this before)
- Problems starting (3 or more tries often necessary, never had this before either)

Secondary diagnosis
- Cylinder #1 misfire
- Head gasket problem, needs replacement

Estimated cost to repair: $2,100

Does this sound like a head gasket problem?
If yes, any estimates on reasonable repair costs? Can you recommend a particular service company?

If no, what problem do you think I have?