I've replaced the HD's in two different Sony models. The newer one was simple (GRT170). The HD (OEM is Hitachi 60GB/4200RPM/2MB Cache) was on the side, you just unscrew 2 screws and it slides out in a frame. I replaced it with a Toshiba 60GB/5400RPM/16MB Cache drive and it runs perfectly.
The older was was more dificult (FXA53), and looking at model numbers this will probably be what yours is like. The speakers are near the LCD. There's a screw holding the plate they are attached to. Unscrewed it and slid the plate a little to the left then it lifted right up (be careful of the wires, they aren't very long!) The keyboard is also on a plate, the speakers were holding it down. I gently lifted up the keyboard (again, watch the wires). Now I had access to the HD. It was held in with 8 screws and 3 braces. Replaced the OEM HD (Travelstar 30GB/4200RPM/2MB cache) with a Toshiba 40GB/5400RPM/16MB Cache drive.
I sold the FXA53, otherwise I'd open it up and take pics of everything if it'd help. I think I saw a FX model laptop for sale on the ATFS/T forum. Might be worth a quick search/PM to the owner of it.
If you know how to install it, I'm pretty sure it'd run. Just be careful and don't force anything. If you are really paranoid or unsure have someone else install it for you. If you open it, buy a can of air and clean it out while it's open!
:beer: