Hi,
Sorry for the late answer...
Typical, language barriers, he.

'Liling, is that a 'gutsjeng'?' 'Nono, that completely other instrument, I have 'goodjen'!'
To keep things short, she indeed plays the gu zheng. She is from Taiwan, and her husband (who plays pipa) is from Beijing, but they have been in Sjanghai, and there is one big street with nothing but instrument shops which should be easy to find. They have heard about master Xu, but had nothing special to report on him.
A study instrument would cost you around 200 Euros, for about 600 Euros, you should have a more than decent instrument. Prices of course go up with more exotic artwork and premium parts.
If there is no price tag on an instrument,
always negotiate when they name the price.
Check if the
case is included in the price! Also ask for the fingerpicks and stands.
Liling said to just take it on the plane as extra luggage, it won't set you back that much.
When exporting, take off the strings and bridge.
That's about it.
It's a beautiful instrument that can produce a wide range of atmospheres from eerie magical stuff, to the darker dissonant moods. Play on either side of the bridge, bend strings with your left hand... I think it can get pretty deep to master...
I'll try and record some parts if I find the time later this week.
The other instrument is not an Erhu, but Gedjek. It's an instrument that is typical to the region of Urguria (occupied by China, comparable to Tibet, and now called Xin Sian (?)) and can only be bought there (as it should say on the bottom of the attachement, only written wrong... me trying to speak chinese, and they trying to write dutch...

)