If you want Sky you need a Sky digibox. Luckily, you can get one free. (just £40 installation cost and have your Telephone hooked up to the digibox) but, the digiboxes are Sky only. There are no cams for Sky.
If you want to watch other digital channels (not Sky) you will need another receiver like the Manhattan.
AFIK the video***** cam is built in and cannot be removed.BTW if you go for the cheap (£40) package, the contractor is likley to fit a mini dish so that you will end up with two dishes (problems with planning permission perhaps?). If you can it may be easier if you can use the lnb loopthrough if it available on your existing Echostar machine and just use your existing dish.
Videoguard is indeed built-in. It is not of the CI type that could be slottted into a CI-receiver such as the Echostars. An Italian provider (Stream I believe) is moving to Videoguard soon (away from Irdeto) so presumably they will force Videoguard CAMs to be built. Whether they will be of the CI type remains to be seen, and even if they are, whether they wold work with BBC or Sky cards is doubtful. 2old