It's not the fish oil, but what's in the fish oil that is good for your heart. The most common number I've run into for studies is 1,000 mg (one gram) of combined EPA and DHA omega-3 fatty acids.
Standard fish oils might require three or more softgels to get that. There are concentrated brands that can lower that amount significantly. Also, if the fish oil is salmon oil, try to get wild-caught salmon oil, as farmed salmon have been rated as having a higher amount of mercury in their bodies.
There are also mixed oils, such as Ross is taking, or vegetable-only oils that also have these omega fatty acids. They take longer to develop the same blood levels, but there is no evidence that they don't work just as well when they get there. The benefit of mixed oils is that they have other omega FAs as well. However, not all of them have been shown to have a positive effect.
It should be considered that people with congestive heart failure do not appear to have a positive effect from fish or other oils, and may actually do worse.
Daily Vitamin E dosages over 400 IU have been linked to earlier death (no explanation given in the study). As that is already way over the necessary amount, that's enough warning for me.
Garlic's supposed benefits have been disproven in several large studies. Fortunately, garlic at least won't hurt you, except possibly for your social life.
Be careful of large, continuing Vitamin D dosages, as it is toxic in high doses. This piece from the Wikipedia about vitamin D indicates something else for our tissue valve people in particular to consider the possible risk of:
http://en.wikipedia.org/wiki/Vitamin_D
Best wishes,