How do I calabratie a Viking gas oven

It sounds like the pilot light has gone out. The thermocouple might have failed. It is a gas appliance so you will need a gas certified technician.

Google

Viking (model) manual

..

Temperature sensor faulty

This did not work for me. The alarm won't go off at all. The dial for the clock seems very loose - it stuck many times when I was turning the dial to change the time, and then it just got loose, and now the alarm won't go off. Please help!

Oven temperature can be adjusted for a maximum of 35 degrees farenheight.
Refer to the page 11 of your owner's manual.
A PDF version of the owner's manual can easily be find at
http://shop.amana.com

It does not sound like the guy is trying to rip you off. Most mechanical thermostats are adjustable by a center screw in the oven control knob stem behind the knob. The problem is when an oven is off by more than 30 degrees they become almost impossible to calibrate correctly and it is better to replace it. There would not be any danger in just using the thermometers and just living with the problem. It would be a very expensive fix for a Viking and if you can live with it then you are better off. The parts alone will probably be over $300 and then there is the labor charges. The thermostat assembly also includes the tempature probes so it requires major range dis-assembly to replace it. Sometimes the oven control knob will have an adjustment screw on the knob istelf(back of knob) to adjust the position of the dial ring to match the correct oven tempature. This can allow you to change the position of the knob to match the actual tempature of the oven. They usually will only go 30 degrees one way or the other though. So my advice is that if you can live with it and are able to still cook properly then put off fixing it. If you find that over time the cooking tempatures start increasing then you might have no choice but to have the thermostat assembly replaced.

Oven temperature sensor, here's a link to the part you need.

http://www.appliancepartspros.com/part_details.aspx?part_id=2023670&pn_=WB21X5301

Temp probe/thermometer inside oven dirty, or off attachment, or defective. On some models, a small screw head adjustment is provided to calibrate thermometer under dial knob. Else, I would just set dial 50 degrees higher rather than expense of new thermometer or dial.

how bad is the temp off?

With a small screw driver and a steady hand. Set the knob to the temp u want then pull knob off. Inside the stem there is a little screw. Try and regulate it slowly also allow it enough time to reach the desired temp. Good luck.

Check the temperature select knob. On the inside of the knob there should be an adjuster.

The temperature probe may be the faulty component since this is an integrated machine.