Hi Frith, apologies that I don't have a full circuitry schematic, sadly I've certainly never seen one available for any Virus.
If you open the Virus, though, sometimes you can see if a capacitor has blown just by looking at it, hence the capacitor layout I gave you. From the various similar forum threads elsewhere, the capacitors that people have seemingly had problems with in the Virus B are the 100µF 25V capacitors, of which there are two - I've highlighted these in the dashed green box:
http://www.infekted.org/virus/images...b-bad-caps.png
Capacitors in general can 'bulge' outwards slightly at the top (or bottom) when they've blown, or sometimes they split, or show chemical leakage in worst cases.
If you take a look and they do look blown and you're not happy with soldering, you could perhaps ask the shop you've been just to replace the caps for you on your behalf, rather than have them do extensive diagnostics. Or you might know of a friend who's confident with a soldering iron, that could switch out the capacitors for you.
Sorry that I can't personally help further. The only synthesizer repair centre that Access tend to recommend is their hardware branch in Germany
http://www.synthesizerservice.de, although I'm unsure how much they charge, with P&P it could be costly.