I have a linksys befsr41 router , and was curious...... is there a certain way to set this up for maximum security?

I don`t have a full understanding of a Nat firewall. as you can see.

On my computer which is a personal home computer i have the linksys switch and norton internet security.my internet connection is a cable modem. I have also seen that alot of people think that norton sucks. Is this true?

I guess what my question is : what should i do for maximum security?
Get rid of norton? re-configure my router?

Hopefully this question is not too newbie...it seems i am learning alot, just not about 1 thing , i jump all over with my readings. I am reading about tcp/ip right know and it is interesting.

Thanks in advance, mike