Go to the tutorials section, there are lots of guides.
The web browser is not built in. It's a 500 Wii points download from the Shop channel, or an illegal wad.
Use a Shop Channel updater to update only your shop channel so you can use it without updating firmware - It's included in the IOS 61 installer, google it, choose the shop install.
If you do update to 4.0, Nintendo can update your firmware while you sleep due to the new EULA. This hasn't happened yet, but even Bushing has admitted it is a possibility, though unlikely.
It cannot render the chip useless, Flatmod is a 4th gen chip, uses intellegent code transfer, so it cannot be detected. The greatest harm updating can do to your system is render all current and future homebrew useless. It does not have the possibilty to brick your Wii, unless it's an out of region update or you have a softmod.
If you have the $$$, go get a replacement DVD drive with a Wiikey2/Wasabi, it has 6x loading times and GC audiofix.
Other than that, there's not much difference, only you can't have Bootmii since you've got a new Wii, with the bugfixed boot1.
Be careful with homebrew, if you completely screw up your Wii, it's not fixable without Bootmii which you can't have!