Volvo Repair: 1983 Volvo DL electrical system / replacement, eletrical system, car work

Question
I recently  purchased a 1983 Volvo DL station wagon. The former owner says that the eletrical system tends to go haywire when it rains: tail lights stop working and  sometimes the car won't start or gets really sluggish - these thing may or may not be electrical problems but it is my understanding that they are related. the clock inside the car work sporadically too.  I was also told that the insulation on many of the wires is getting old and crumbling off. Since I purchased this car from a friend I also know that this car also seems to blow fuses more often when it rains.
I did a general web search and have found some pages that claim rewiring the tail light etc is fairly simple but no actual inormation on how to do it. I am planning on buying a repair / service manual but I wondered if you had any recommendations or advice in the meanwhile or any useful web link or book recommndations. I have some knowleedge of general electronics and wiring but this is my first car and I have never done more than change spark plugs ona  car before so I am not really sure where to start.
Thanks for your help  

Answer
The first thing I would do is remove all the fuses and clean the connection and replace with all new fuses.
Tail lights not working is usually just a loose or poor connection at the light, try tightening it, by crimping the connector tighter.
Clock inside not working is its own circuit, check the ground connection.
These cars did have wiring problem with the engine compartment harness. Look at the firewall and look for a harness with worn insulation. Just replace each wire with new.