'91 200TQ fuel pump - Bosch part number?

[Bart Oleksy]

I was the one with the hard starting problem when the car's "cold"
(which I mean sitting for more than 15-20 minutes - the longer it sits,
the harder/longer to start).  I had a mechanic look at it (he used to
work for the local dealership but is now on his own) and he saw that the
fuel injectors were leaking (so he put in some additives) and that I
need a new fuel pump check valve which he ordered for me.

However, he was concerned that my fuel pump is quite noisy, and that
once the check valve is replaced, the fuel pump might 'go' (increased
pressure or something), so it's one of those "while you're in there..."
kinda things.

I did find a place with a Bosch fuel pump, new, for $130 U.S. plus
shipping, which beats to hell my guy's local price of over $400 CAD.
But I'm just trying to double-check that this cheaper one is actually
the right one before I place the order.  He was giving me these part
numbers:

0 580 254 040   or
0 580 254 042

What's the best resource (other than bothering so many of you mailing
list members) to double-check such things?

Should I also be replacing the fuel injectors as well, or is that a
separate item, not so related to replacing the pump and check valve?

Is there even a cheaper source for new fuel pumps?

And I also found a good price on a Pierburg - is that better than Bosch,
worse, the same?  Fits the same or different?  My mechanic is familiar
only with the Bosch products, so he was a little skeptical of some other
brand.

Thanks for any and all help on these questions!

Bart
1991 200TQ
1986 CGT