Plumbing in a nutshell - Wikipedia
Quick definition of "plumbing", provided to us by Wikipedia
Plumbing is the system of pipes, drains, fittings, valves, and fixtures installed for the distribution of potable water for drinking, heating and washing, and waterborne waste removal. "Plumbing" also refers to a skilled trade which deals with installation and maintenance.
The plumbing industry is a basic and substantial part of every developed economy. The word derives from the Latin plumbum for lead, as the first effective pipes used in Roman era were lead pipes.
"Plumbing" often denotes the supply and waste system of an individual building, distinguishing it from water supply and sewage systems that serve a group of buildings.
Plumbing - pipe types
Constructing your plumbing and drainage installation, isn't as straightforward as it may seem. First thing you need to choose, is what type of pipes are you going to use? There is plenty to choose from, but not all are multi purpose and good for your home.
Generally speaking, you need the ones relatively easy to install, repair if needed and with long life span. Price is also relevant, of course, but sometimes it is better to pay up more up front, rather than upgrade it later.
The answer to such problem is only one - PEX pipes. You might thought that copper pipes are better, but they aren't - harder to install and much more expensive. All in all, pipes from PEX are very good, either for the plumber or user. The only thing that's left, is to find were you can get them cheapest, and in required diameters.
Boiler repair - call in the specialist
There are repair jobs, that almost anyone can do themself, but broken boiler isn't one of them. Boiling hot water and immense pressure - those are the things that define boiler, and also the things you should be wary of.
Calling in professional plumber isn't any shame in this case, it is necessesity. It is different from a ticking bomb, but close enough, especially if the safety valves are at fault. All in all, you need expert on this - let him do his job, and relax. He is aware of the risks involved and already knows how to avoid any mistakes. All you need to do is coffee and maybe some snacks, while he do his job.
If you are not convinced by this, and ready to repair you boiler alone, all i have to add is this: search the internet for movies of exploding boilers, I dare you.