Very experienced. In fact, my own dog, a 12 year old Cocker (no kidding), just had his spleen removed due to a bleeding tumor in it.
Now, here's the difference. Certainly, there was cost savings since I did the surgery. More importantly, there was no evidence of other disease (like the enlarged liver) at the time of the surgery. He is on chemotherapy now.
What's the difference?
Well, the enlarged liver is very concerning.
What we really need to know is if the liver is enlarged due to a concurrent condition, or if there is already metastatic disease throughout the liver.
The sonogram doesn't sound like it was that detailed. If it was not done by a specialist (a radiologist or internal medicine specialists), I would hold off surgery. Absolutely, get a referral to a specialist ASAP for a better ultrasound. In addition, if things are still uncertain, a needle aspirate can always be taken from the liver and/or spleen to try to identify what is being dealt with.
Unfortunately, a common cancer to be in the liver and spleen is hemangiosarcoma. It is a bad one. If you are not really thinking of chemotherapy, personally, the surgery would not be worth it. Without chemo and having that particular type of cancer, the statistically life span is 2-3 months. With chemo can be up to 12 months, but that is without evidence of spread to other organs.
I would get a second opinion before surgery.