Hello all!

I am new to the forum, but excited to see if anyone can help me.

I just bought a 2000 350 Mariner and after one week I found a really bad vibration coming from the port side while underway over 2500 RPM. Anything below 2500 RPM is smooth as silk. I brought her to the ship yard to be hauled out for a quick check of the props and drive lines. After inspection, the props are good, drive lines are straight, cutlass bearings good, but found play in the port side gear when turning the props. The mechanic at the shipyard says that the gear needs to be pulled and looked at (Rebuilt/Replaced). I have a couple questions below I am looking for advice/answers on.

1- Does the motor need to be pulled in this model Carver to get the tranny out?
2- I cannot find the data plate anywhere on the transmission to get model/serial#. What is a good number to call Carver direct to find this information out??
3 - What is a typical cost for a job like this, rebuilt or replace transmission?

Thank you all so much for taking the time to read this and help me out.