Extend Time Capsule Wireless Range

I am having trouble with my Time Capsule's wireless range. I am not a networking expert by any means. I own an old building that is 4 stories connected by stairs with thick walls. All the rooms ethernet cables converge in a cubby on the 3rd floor. I placed my Time Capsule in the cubby, but I couldn't receive a wireless signal from the 1st floor. This is ironic because I have an old Netgear G router that sends signals throughout all 4 floors. So I bought an Airport Express to extend my network wirelessly, but the signal has been unstable perhaps because the Time Capsule's wireless signal is too weak. So I want to connect the Airport Express on the 1st floor using the Ethernet link from the 3rd floor Time Capsule which is my main router. From my research, I discovered about WDS networks, which I believe you have to use in order to create a network with multiple Apple base stations linked through ethernet.

I called Applecare who told me:
-To connect from Time Capsule to Airport Express using Ethernet, must use WDS network. Setup Airport Express as Relay, NOT Remote.
-Relay- Direct ethernet connection from Time Capsule to Airport Express, then wireless connection from Airport Express to Macbook.
-Remote- Wireless signal from Time Capsule to Airport Express, then direct Ethernet connection from Airport Express to Macbook

I have several questions for you wise people out there:

1. To extend the Time Capsule wireless network using the Airport Express, but connected directly via ethernet, do I need to setup a WDS network?

2. I prefer to just use the simple Apple settings "extend network wirelessly". Will this setting only boost a wireless signal received from the Time Capsule? Can it not extend a wireless signal sent directly from Ethernet?

3. I'm considering getting a Quickertek Triband antenna to place outside the cubby. Anyone have any experience with Airport external antennas?:
:: QuickerTek :: Antennas :: Time Capsule Antenna ::

Any information would be much appreciated! These networking issues have been giving me months of headache.

Thank you!
Alexander

Specs:
Apple Time Capsule 1TB
Airport Express N version
Connected with 2.4ghz. band to N capable Macs.