Some questions from a new reader ...

My '87 Westy Weekender has broken two water hoses in the past six weeks and 
had a cracked coolant reservoir. I was wondering whether it would be a good 
idea to replace all the hoses now or just keep fixing them as them break? 

The dealer gave me an estimate of $550-$600 parts and labor to do them 
all. Says there are about a dozen hoses from $15 to $55. He can have it
in and out in two days, though if I order just the parts it'll be 3-4 days. 
Austin VeeDub, who sounded like they didn't really want to do the work  
("Too many damn hoses on that car." :), ballparked it as $600 in parts. Is 
the dealer estimate reasonable?

Also, someone mentioned a blown head gasket would cause water hoses to 
break due to increased pressure. Why? I've notice no decrease in performance 
or watery exhaust, though I have the common Vanagon water leak from the
cyclinder heads that I've temporarily stopped up with AlumaSeal.

All responses appreciated. Thanks!