This is a very simple operation. You will need to purchase a replacement pump with identical or similar qualities. The electrical connection is generally a pre-wired 13- amp three pin plug that is simply being plugged into a convenient socket outlet, therefore there should be no problem with disconnection and reconnection. If you are not confident to carry out this work on your own, you should call a professional plumbing service such as Abbey Wood Plumbers who are qualified to carry out such work. Once you have everything at hand to the task is completed as follows:1). First, isolate the hot and cold water to the unit and confirm that it is off.2). If available, open the drain off cocks to release any water from the pipework feeding the pump. Alternatively, be prepared for a little water to discharge as you disconnect the pipework. Fortunately these connections are usually made by a flexible connection with push fit compression joints, your new replacement booster will almost certainly have the same sort of connections. So it is often simply a case of removing the old connections and fixing on the new ones, as the flexible connections will allow for the necessary free movement to facilitate the replacement.3). Turn on water supplies and check for any leaks.4). Plug new pump into the socket outlet provided for the existing pump.When no flexible connections have been provided you will have to be prepared to alter the pipework as necessary, taking care not to damage the plastic water connections of the new pump with heat from any soldering processes or cross threading the connection. The above is basic advice, and again if you don’t feel confident to carry out the work yourself, call a plumber such as a Thamesmead Plumber who is experienced in this work.