Toyota Repair: Toyota Camry 92 steering shaking, spark plug wires, drive axles

Question
Hi Ted,  I have a 93 Toyota Camry 4 cylinder, 200K miles auto. After going throught previous Q&A I've think my front engine mount need to be replaced.  Here is the symptoms,  engine idle smooth but when engaged in D-drive or R- reverse, the steering kind of vibrate a lot.  I have already replaced the torque mount, the one next to the timing belt cover, which doesn't help.  I think I am going to try to replace the FRONT engine mount and hopefully it should help a little.  Would you please tell me if there is a possiblility that I have to replace the REAR engine mount as well.  It is very difficult to check visually which one is bad.
By the way, how often should I replace the spark plugs wires? How often should I replace  a new water thermostat?  If I have to replace the water thermostat, is it possible I can use a after market one or I have to use the Toyota factory one?  What about the axles both RH and LH, when should I replace these?  Now the outer/ inner boot is fine.  Sorry I've asked you too many questions but these are the concerns that I have and thank you for your advice.

Answer
The rear mount almost never causes a problem so go ahead and try replacing the front one, by the way do you know if the car has been in an accident? There are no specific intervals to replace any of the items mentioned, the thermostat should be replaced any time that any cooling system repair is done or in case there is an overheating concern, the difference in price between genuine a toyota thermostat and aftermarket is minimal so I would stick with the one from the toyota dealer, if the spark plug wires have never been replaced I would suggest doing them, if the wires are original or factory replacement wires they will have a date imprinted on them, if they are more than five years old I would suggest replacing them, Toyota drive axles are extremely durable and almost never need to be replaced as long as the CV boots are not broken. If and when the boots do break and the grease leaks out replacing the boots and putting in new grease is all that is required.