[V8] Imminent Fuel Pump Failure?

[Gunter Lorberg]

One of my '90 V8's fuel pump just started to make substantially more noise today.  Car has about 180 000 miles on it....to the best of my knowledge pump has never been changed.  Pump was previously slightly audible.....now it is clearly audible...it is worrisome.  Performance of car seems unchanged.  The noise became noticeable at the end of a lengthy day trip totalling about 200 miles.  I changed the fuel filter several months ago.

My questions to other listers:  
- how long have I got before it fails completely?
- What are common signs of failure? 
- There seem to be two available through online suppliers....one's a Bosch....the other a Pierburg......will both work?....anyone out there have an opinion on which one is better?  Should I buy dealer supplied instead?

Thanks
Gunter
(2) 1990 Canadian V8's (automatics)