Hello Philius and welcome.
I have moved your post to the correct forum for you.
Its a shame you found us now as you probably would have obtained a better price through a sponsor and you definitely would have received better service ::)
Two issues as I see it:
First the taste-
Taste the water out of the machine to be certain its boiler taint you are tasting and not something else which has changed.
Secondly, the replacement boiler-
I hear that there has been a batch of dud boilers in 2010 Silvias. A tech I know suggested up to 20% of machines have suffered from element failure pretty much out of the box.
A competent tech can tell the difference between a cooked element (your fault due to failure to prime the boiler) v faulty element.
I suspect your no bricks and mortar, no service we just shift boxes establishment has assumed the former and hit you in the hip pocket accordingly ::)
Let us know how you go....