This is definitely the mechanic's responsibility.  It may not be his fault, though...

Mike B.
  ----- Original Message ----- 
  From: Jeff Gellman 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Wednesday, December 30, 2009 2:39 PM
  Subject: engine issues

  hey all

  I write this as my 1989 VW Westy is in my driveway undrivable for the 2nd
  time this year..I had an rebuilt engine put in about 10 months ago after
  driving 160,000 on the factory engine...not sure where my mechanic got if
  from but I saw it come out of the crate and it was a nice rebuilt one..so
  about 20K into it, which is about 8 months for me a coolant pipe blew and I
  did not realize it until I got off the highway and lots of smoke and then I
  heard the little red light and alarm going off onthe dash that told me I had
  engine problems..well..i melted the inside of the engine (that is what I was
  told)...so after my mechanic looked around for something to put in he found
  another engine..it was not rebuilt though..just said it was a decent
  engine...well... 2 weeks ago it was done...I drove down to NYC from PVD 180
  miles and then on my way back I lost engine compression about 30 miles back
  into my return trip...I looked underneath and saw the oil pressure gauge
  thingy hanging by the wire...the oil pressure gauge was put in by the
  mechanic along with an aftermarket gauge on my dashboard...after careful
  looking it looks like the pressure gauge thingy was broken off about 1 inch
  from the end with some threads still showing...

  so...is it possible that when it was installed it was not put in the correct
  place? was it torqued to tight and the engine vibration dislodged it? pretty
  much by this coming off my engine is destroyed...so after spending 4000.00
  dollars i got 2 weeks worth of driving...I find it hard to believe that this
  is my fault...should the mechanic be taking responsibilty for this?

  --
  Jeff