D-Link DGS-1210-16 setup with WAN

Considering purchasing a DLink DGS-1210-16 and am wondering if it is possible to configure one of the ports as WAN input?

Also would anyone know what kind of speeds they can get with this switch. Close to the 1Gig when you have fibre?

Well, it's a switch, so has no notion of "wan" or "lan". It just shuttles packets between ports based on layer 2 addresses...

"Possible", from a purely academic point of view, "yes'ish".

No, not at all, far from it (~15 MBit/s max), it's a switch, not a router.
The switching is handled within the switch fabric, offloaded to hardware (the mips 4k CPU is not involved with that), you get the full wire-speed of your switch fabric - but for routing, the 'companion' CPU of the SOC is totally inadequate.