Yes, the HDHR will try to obtain an IP address via DHCP (from your router usually), if that fails it will default to a 'net-local' IP address. If the wired NIC on your laptop is configured to do the same, the two devises will be able to communicate. This method takes some additional time to start working initially because the DHCP process has to timeout fist. You don't need a WiFi signal for this to work.
Just remember, the only thing between the antenna and HDHR should be a short (10' or less) coax cable. You want to have as little loss from the antenna to the HDHR. The same will be true for the preamp when you get to the point of reinstalling or replacing it.
I'm certain the PA-18 will outperform any RS amplifier. But, think of a well as an analogy to the antenna... would you expect to get clean water from the tap if you installed a high quality, high pressure pump in a hole that had just a bit of muddy goop at the bottom? Obviously, the hole is not an effective well unless it is deep enough to reach a steady supply of clean water. If RS will still accept the amplifier for refund, I would take them up on that... the $70 may be a valuable peace offering to your wife. the PA-18 is available through Amazon for about half the price of the RS product.
http://www.amazon.com/Antennas-Direc...8+preamplifier