The complexity of installations varies enormously. For example, if you want to install a small fixed dish on a house wall with easy access from a flat-roof garage, you may be able to install it yourself or with a friend. You will need to have lots of patience, preferably be fascinated by the idea, and competent at using power tools so that you can drill holes in the outside wall. Or you may have a flat roof with easy access.
But don't forget that dishes can be heavy and must be fixed securely so that they can withstand even gale-force winds without falling or being knocked out of alignment. Although the dish does not need connecting to the mains electricity, it is important that the low voltage and signal connections are secure and sealed against the ingress of water.
You also need to ensure that your installation meets local authority requirements, especially if you live in a listed building, conservation area, or other "special" situation.
Astra SES provides an excellent guide to satellite dish positioning and installation "Astra DIY Installation". It is suitable for satallite dish installations throughout UK, Europe (Western, Central, Eastern, Northern and Southern Europe) and parts of North Africa.
See also How to align a satellite dish.