Don't be shy about using the search functions - most of your questions have been answered many times in the past.

W123 front ends seem to need rebuilding every 175-250K miles. It is not normal for any of the rubber boots to be cracked. The front end work is not difficult but it is heavy, dirty and potentially dangerous. You will need a fair share of specialzied tools (spring compressor, ball joint press, tie rod seperators, ect)

IMHO this is not a good job for a beginner DIY'er - if you don't know what the above mentioned tools are or how to properly use them I'd find a more experienced mechanic to help you through the process or let a pro do it.