I think washing it and trying out the advice from Cheryl's link that she posted might be your best bet, unfortunately. My friend once had dr. pepper spill in her knitting bag and it stained the silk yarn that she was knitting a project with. Soaking it made it better, but there were still stains that were noticeable. She ended up overdying the yarn in the end, something you could also do if you are feeling adventurous :)
Catrina, you may want to try the children's detergent "Dreft", or even "Biz" bleach (a non chlorine bleach). I used to use Dreft all the time when my kids were very young. It was great at removing stains and not harsh on the clothing at all. As for the Biz Bleach - an antique linens dealer suggested that to my sister as a gentle way to remove stains from very old linens. I have also found that to be fairly gentle. Hope you are successful in removing the coffee stain.
Oh goodness, I hope I can remember all the things I said. I couldn't get the link button to work. Then when I clicked reply, the link came up but everything else I typed was gone. So let's see if I can say something close to what I said before.
Susanne, gauge is important if you are doing a garment or want your project to be a certain size. Many of us hate doing gauge swatches, including myself, but we also know when it is important to do one.
You might want to look at some of the knitalongs. You will find lots of wonderful knitter in the knitalongs who can be very helpful. It is easier for us to help if we have a more specific question. Please give us a try before you give up. Either go to the top of the page where it says Meet and Share and click on knitalongs or click here
We actually just did an entire podcast on gauge! You can listen to it here, that might help a bit :)
ETA: Good idea, cheryl! The Learn to Knit KAL might be useful too.