There are several "rules of thumb" for the proper valve spring pressure on different types of camshaft configurations and types. Setting up a cylinder head with the "correct" valve spring pressure is a relatively simple and cheap method of increasing engine performance. One thing for sure is that you have to check the seat pressure and open pressure as both are critical. It is possible to have the right amount of spring pressure when the valve is on the seat and too much when the valve is open and vice versa. The only way you can determine whether or not the springs you have will work is to properly measure the "installed height" of the valve spring when the valve is closed and check the springs with the retainer installed on a valve spring tester. This is the distance between the bottom of the valve retainer and the spring pad. The easiest and less expensive way to measure this is with a snap gauge and a set of calipers or micrometer. One you have this measurement you can properly set the installed height and determine if the open pressure is enough or too much. As for breaking the camshaft, this is a very rare occurance if you do it correctly.
For disassembling the valve springs on a cylinder head, the proper way is with a spring compressor but there is an acceptable alternative to this. They make a tool that is magnetized that is specifically for keeping the valve locks from "flying everywhere". This tool is relatively inexpensive and is made by KD tools I think. With this tool, you use a hammer and when the spring is displaced enough, the locks "fly" up into the magnetized hole that holds them in place. This tool also comes with another piece to allow for re-assembly.
