I also have the desktop upstairs to which the printer is connected, and would like to print from the lappy downstairs...
You can Share the printer on the desktop and then print to it over the network from the laptop. Obviously both the printer and the desktop PC have to be on.
You can buy standalone network print servers (including wireless) which will do the job, but they don't really work with MF devices (apart from basic printing), nor do most support bi-directional capabilities (status reporting and other printer functions).
is there any way to WiFise an external HD
Again, if the desktop to which the USB hard disk is attached is switched on, you can share the hard disk and access it over the network from the laptop, just like sharing the printer.
There are some wifi router / access points that have a USB connection for an external hard drive (I had a Netgear one for a while, but didn't think it was all that great). You can also buy dedicated NAS (network attached storage) devices. You can even just buy the enclosure and add your own hard disk - like
this.
SD