A6 won't start. It has a ton of miles (244K) and I suspect it might be the fuel pump. History:

Bought for wife 6 months ago. She only drives 2,000 mile per year.
Was running fine but took a long time cranking to catch. (5-10 seconds). Once running, it was fine.
The long crank wasn't a show stopper but was annoying

Fuel filter changed (was very dirty)
Replaced emission control valve
replaced coolant temp sensor
Chased down various nasty vac line and replaced
None of this helped
As it turns out the internal fuel pressure check valve was bad. Without holding residual pressure, it took linger to start.

Since the check valve is part of the pump, I couldn't replace it. However, I found a $20 / 30 minute fix. I added an -in-line check valve (brass with industrial chemical safe). That was 3 months ago and it's been starting regularly since then.

Now, it won't start at all and I suspect it's the pump. I haven't checked the fuel pressure yet but plan to get a gauge and do it tomorrow.
I think I'll need to tee into a line somewhere cause there is no port. (any suggestion as where to tee into it?)

Ok let's assume it's the pump. Going back 6 or so years, I paid big bucks to have a fuel pump put in a 2000 A8. The damn pump was $800 by itself. I kept the old pump assembly and learned that the actual pump inside the assembly could be replaced. It cost $200. I cleaned up the big assembly, put the internal motor in it and put it on the shelf. Last year, I had a shop put it in a 98 A8 my wife was driving.

Now I'm looking at pumps for the A6 and if the pump is bad, thinking of replacing it myself (this because I would have to get my big body in the trunk like with the A8) Googling suppliers I find prices as low as $105 bucks or as high as $500. What's the deal? Is this a pump in a pump? Can i just replace part of it?

Any advice welcome.