[Yorkieluv]

I am sorry your baby is sick...

Just like TLC said, your first step needs to be a bile acid test, a full blood panel including a CBC, and a urinalysis to check for crystals which is secondary to liver issues. If they find ammonium urate crystals or stones, it is almost guaranteed to be a liver issue because they only form in Dalmations or dogs with PSS.

A bile acid test is necessary because it is much more sensitive to liver function than a regular blood panel. A blood panel is important so you can check her ALT, ALB, BUN, etc.
Next, if those are elevated, your vet might suggest an ultrasound..If he wants an ultrasound to check for crystals/stones in the bladder and to check the size of the liver, then it's worth it, BUT if he's solely looking for a shunt, regular ultrasounds are not very reliable for that.

U of T prices have recently gone up to around $1800 from what I have read.

But at 3 yrs old, you really have to decide if it's better to have the surgery or medically manage the dog. The older the dog, the higher the risk, especially with portal hypertension which can happen after the surgery.
If it's a single extrahepatic shunt and nothing else, surgery may be a good option...
If it's several shunts, they cannot be repaired and need to be managed medically and with appropriate nutrition.
Even if it's not a shunt, it could be MVD, which also cannot be repaired and needs to be managed medically and with appropriate nutrition.