I think it's wise to try to keep all your gear dry - whether or not it's supposedly weather sealed. Your warranty does not cover water damage.
Most important - Do your best not to change lenses when there's rain about - it will get into your camera. If you absolutely have to, you need a large clear plastic bag, a tea-towel to dry everything, individual bags for your lenses and easily accessible body / lens caps. Then you need to practice what you're going to do before you try it in rain. Having three hands helps to stop you dropping something in the mud...
On the DIY approach - a large plastic bag, a couple of a elastic bands and a pair of scissors are all you need. The real trick is not standing in the rain... so get an assistant to carry a golf umbrella for you. Since the ground's probably damp too, it can help if you and your assistant have a monopod and a Walkman seat.