can you help me tell if my lens is dirty or is it my sensor?

see the dark spots on the picture?

 

That's your sensor. Get a [ame=http://www.amazon.com/Giottos-AA1900-Large-Rocket-Blaster/dp/B00017LSPI]Rocket Blower [/ame] and start cleaning.

 

I did open up the sensor and used a rocket blower. should i go to a brush? if so can you recommend a good one?

 

Because using a brush can and will void your warranty if you damage the sensor, my inclination is to have a professional cleaning service do more heavy duty work. But probably there is someone who can give you brush tips.

You are putting it in sensor cleaning mode, right?

 

Yep. I lock the sensor. Blew the sensor area with the rocket air.
seeing that the brushes are like $40... how much is a sensor cleaning (roughly) for a canon 40d.

Thank you for all your help guys!

 

My sensor cleaning on my 30D (included complete cleaning of the body) was about $40 locally.