[TR] TR4 wiring

[Gary O'Hagan]

List,
Please bear with me . I am continuing on with my wiring . This is not 
my strong suit and I am making this a lot harder than it has to be.  
TIA.
1) My fuse box disintegrated.  Should I use an original type 
replacement or is there an advantage to using an upgraded blade type? 
If I upgrade what exactly do I need? Know any sources for these?
2) There are two wires that come out of the heater box. Does one go 
directly to the switch and the other to a ground?  There are three 
prongs on the blower switch, what are the other two prongs for?
Gary O