Not heatig up just cold air

If the dryer is blowing air, then I'm assuming the drum is turning. If this is the case, the following link explains how to diagnose and correct an electric dryer no heat problem:

http://www.fixya.com/support/r630242-dryer_runs_but_not_heat

This is an ELECTRIC dryer, correct? I ask, because you posted this under GAS dryers. Pay particular attention to the section that discusses proper ventilation. Most dryer heat related problems are caused by poor air flow due to clogs in the vent ducting. Cleaning the lint trap is not enough in most cases. You need to also check the ducting and dryer interior from time to time. Clogs in the ducting actually forces the dryer to work harder and causes the heating circuits to overheat to the point of failure. Not to mention...this can be a fire hazard! If you cannot remember the last time the dryer ducting was inspected or cleaned, now would be a good time to do so. Leaving a dryer in a clogged condition will cause premature failure of any parts you may replace.

To answer your question, "No", this generally does not cost a lot of money. All the heating circuit parts, combined, would cost roughly $100 or less (if you had to replace everything). This is also a fairly simple repair that the average do-it-yourselfer can accomplish on their own.

Read through the link thoroughly and let me know if you have questions. If you require additional assistance, please let me know before you rate the solution. I hope this helps you.

PS If this was intended to address a problem with a GAS dryer, please let me know so I can correct the diagnosis for you.

No replace the element or the thermal limiter also called the thermal fuze