Yes if you have your PBX loaded with operational software on it.
You can use the GUI and HTTP protocol or TFTP protocol to make software update.
As a first step put the uImage-xxx-md5 file so it is http visible. (alternatively tftp visible)
In the PBX GUI go to 'Firmware upgrade' (in the advanced options section) and select HTTP URL. You can reset or keep the PBX configurations using the provided check box.
You need to specify the full path and file name for upgrade including 'http://'.
If you prefer you can update uImage using TFTP protocol instead of HTTP. In this case please specify the IP/host_name of your TFTP server.
You need to specify the uImage file name as well.
The actual software update will happen on the next reboot of the PBX.
This one should be ok. For serial port, either your MB has a built in com1, com2, etc or buy this to emulate.
You also need hyperterminal from XP or puttytel (free) to monitor the serial console output