I am not a professional and no way will give any guarantees or warranty. Like you I own this model of router. Pretty much I tinker with computers and components a lot.
The best possible way to answer this is to this question is to update the firmware.
Question 1:
Since you have a router attached to your cable/DSL modem, your internet provider (Comcast, Cox Comm, etc) more than likely won't help you out. It won't hurt to ask. But the best way to answer this question is to ask someone who seems to know, or pay a professional.
Question 2:
1. Go to :http://www.dlink.com/products/?pid=DIR-628&tab=3.firmware
2. Download the latest firmware and unzip it.
3. Log on to your router and select the Tools Tab.
4. Select the Firmware Option on the Left-hand side.
5. Then, in the middle of the Firmwares option, "Firmware Upgrade" Select the browse to find where
you unzipped the firmware you've downloaded.
6. Select the ".bin" file, normally you hit the Ok button
7. Once you've selected your file, click on the "upload" button.
This will flash the router's firmware. Read all the information that you see. Normally it will do it's thing and reboot itself. There will be a warning where all the settings will go to default (like when you first purchased the router). You need to be familiar with setting up the router after this step.
If all this sounds complicated, you'll need to find a "geek" or a computer savy person and ask them for help. If all else fails call up Geek Squad or any equivalent service. Remember the saying, "You get what you pay for." I hope this helps in any way.