at how many times should a timing belt be change? is it easy to do by yourself or do u need a professional to do it? average price on it?

 

i would change it every 90,000 miles...

if you have never changed a timing belt, i would take it to a mechanic.

 

I think the mileage should be at 90k for the change. I changed mine later, but why risk it. This is not easy to do if you don't have much experience, but if you do it anyways with a good Helm's manual, you'll be a lot more comfortable with your car later down the road.
A garage might charge several hours labor, plus parts including pump and new tensioners and two belts is around 200$. Look in classifieds here - prostreetonline has good deals. If you have a good place to work, and an extra hand, you can finish it in one day, even if you've never done it before.

 

remember to replace the autotensioner or convert it to a manual one