Ethernet Shield and I/O pin question

I am new to the arduino world. My first arduino project will be connecting up a mega 2560 to 48 SSRs to control some christmas lights.
I think I have that part mostly figured out...

I'd like to be able to hook up an ethernet shield to my mega 2560 and have both ETHERNET AND 48 digital output pins.

Will the addition of the ethernet shield reduce my access to the digiatal output pins? The board has pass thru pins
for everything... BUT doesn't the ethernet shield need some of those I/O pins that are passing through it for
communication?

It's a V1.1 Arduino Ethernet Shield. There are 6 ISCP pins on TOP of the board, next to the reset button, but they
do not extend downwards, so when you plug the ethernet shield into the arduino, the ISCP pins on the arduino board
are not used.

Any info would be appreciated.

The w5100 uses digital pin 10 for the SS pin.
The SD card reader uses digital pin 4.
The Mega uses digital pins 50-53 for the SPI interface, so you can't use those for anything else.

If the ethernet shield has the ICSP connector, it must be on the bottom of the shield. See pics here:

If the connector is on the top of the board, it was installed incorrectly. You have a choice:
resolder the connector correctly
or
jump the pins to the ICSP/SPI pins on the Mega