Because of the color accumulation on your ends, I would leave this to a color specialist. It may take a couple appointments to achieve the right shade because of the fact that the specialist only has the roots to go by. If you don't want to strip your current color, you can always go in with a heavy full head of highlights and gradually work your way back to natural as to not excessively damage your tresses. Make sure to use a mask and get regular trims in between lightening services.

get it stripped at the hairdressers, or buy something to strip the color but not a cheap one or you can get another hair dye from the shop and dye it golden blonde x

(thought it does say on the site not to use it if you use straightening/curling irons that go above 200 degrees...)

You can buy Colour strippers - I think the one that I've seen most highly recommended is Scott Cornwall Hair Colour Remover... hope that helps!
Let us know if you use it how well it did the job!
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I would recommed using Henna Cream coloring to you. It doesn't damage the hair, and your hair is probably already damaged. You can pick out a shade on Amazon closest to your natural color, for about ten dollars. Try this brand: SURYA Brasil.