The first thing is to watch your diet, but you probably already knew that even before you posted your question! That being said, I recently heard...can't remember if it was from a doctor or from a continuing education program (I'm a pharmacist)... that your cholesterol level is only 20% determined by diet. For me, having a strong family history of heart disease, being 44, and having LDLs in the 150s, it was an easy choice to go on Lipitor. If you don't know what the different numbers (LDL, HDL, TG) mean, have someone explain the breakdown to you so you know exactly what you're trying to reduce. Different kinds of cholesterol respond to different meds/supplements.
Fish oil is probably the number one recommendation I would make, as long as you have no ethical (vegan, vegetarian) problems with it. I hate the taste of fish, but have found that there are some varieties out there that I don't notice the taste as much. Be sure you take it with a meal that has a decent amount of fat in it, and that will help. I stick with the good brands. you pay a little more, but with the risk of mercury in fish products, I feel more comfortable paying the money to have a pharmaceutical grade product.
Flax seed is recommended as well. You can get the ground flax and add it to many things... oatmeal, cereal, pancakes, smoothies... or you can get the supplements. Be sure any supplements are cold pressed.
Niacin can work as well. Keep in mind that if you take it, particularly the immediate release version (as opposed to sustained release), you may have a problem with flushing. Taking a baby aspirin 1/2 hour before can help, as long as you have no contraindications for aspirin. If you have any plans to get pregnant, please take with you OB first before taking any meds, OTC or not. Flax seed is fine, and I took fish oil throughout my pregnancy.
As far as food...oatmeal can help, but try the plain oatmeal and not the sugary kind, since you want to lose weight. Low- or non-fat dairy products, lean meats, lots of veggies. The diet may not be enough, though, so don't be discouraged if it doesn't bring it low enough. Hopefully, as you lose weight, the cholesterol numbers will drop as well.
Good luck. As a side note, if you need to increase your HDLs and you like wine, red wine has been shown to improve those numbers!