No problem. Once you get your feet wet, then move on to the tougher to get accepted ones. Sounds like you have the drive, if you keep at it you will soon be submitting to all the sites.
As to your photoshop question, yes, definitely. I almost always use photoshop to remove some items in a photo. Whether it is a logo or a distracting item. Just be meticulous about it, because you don't want the removal to be noticeable. The rubberstamp tool is great for doing this. The pen tool is great for doing white backgrounds. Takes a bit to get the hang of it, but once you do isolations are easy. For the most part items in photos are fine with no brand name/logo. There are some weird exceptions to this. One example is Crayons. The Crayola brand crayon trademarked/copyrighted the wavy lines that are on the paper on each crayon, so this can't be displayed in a photograph you sell without a release from Crayola. Istock recently made a new rule on submissions that show a car, since cars are so easily recognizable. My best advice is to read through the faq's and tutorials on each site you upload to. They will help give you a good idea of what can and can't be accepted. When in doubt, submit to one of the critique forums and ask members what they think. Many sites have members that are very knowledgeable and helpful.
Happy Downloads!
http://www.sprintingturtles.info