Yep get the sensor cleaned.
Sorry for being ignorant but is that a job I can do my self? I have a Canon 400D.
But it all depends on how confident you feel.looks like dust bunnies to me
high aperture (judging by DOF on your picture)?
try another lens with f/22 and see ifmuckartefacts are in the same place
You can do it yourself,its not a big job, google it or have a look on youtube.Sorry for being ignorant but is that a job I can do my self? I have a Canon 400D.