I am not a doctor but from talking to my dad's doctors on the issues you raised, here are some thoughts for you and questions for your doctors.
1) Pathology result of tissue is the most reliable indicator of what a tumor is (benign or malignant, and type of malignancy). While some diagnostic radiologists can tell what a tumor is from looking at scans (CT/MRI/PET CT etc.), even they will say it usually is not with 100% certainty until confirmed by pathology work. Having said that, since you already have multiple scans, and a MRCP coming up, you could get copies of those scans and ask for second opinoions from multiple radiologists, especially ones familiar with liver tumors, to see what they say. You would want to know if the tumor is i) benign vs. malignant, and ii) if malignant, with how much certainty is it cholangiocarcinoma or hepatucellluar, or something else.
2) Seeding is a concern in biopsy, but multiple doctors have told me that the likelihood of it is very small. You'd want as experienced a doctor to do it as possible so getting it done at a major hospital is worth it and likely decreases the chance of seeding happening. The percentages quoted on the internet are averages that don't take into account the quality of care of different institutions so the numbers can be misleading.
And as a personal anecdote, my dad's tumor was ~5cm when it was diagnosed and his surgeon at UCLA (Dr. Busuttil) recommended resection right away without a pre-operative biopsy. I don't know if that is conventional or not, but the diagnostic radiologist felt strongly the tumor wasn't benign so from the surgeon's perspective, given the size, it made sense to remove it sooner rather than later, and biopsy with pathology results afterwards, which indicated it was intrahepatic cholangiocarcinoma.
Hope this helps.