Here are a .jpg with the pin layout of the converterbox for Mr. Handsfree.
The diagram is not complete, but this is not important as it is only the pin connections which are important.
The right side is the RJ 45 plug's wire colors and the left is the plug for the phone.
If your 8110 has the 2.5mm jack connector then I will guess it is connected to pin 3,4 & 5 on the phone side of the converter.
My Nokia 6210 has a different connector than the 8110.
I dont think it is a good idea to connect the MDA directly to the RJ45 connector as there was some noise generated from the phone. The noise disappered when the MDA was connected on the phone side of the converterbox.
At some point in time there will most likely be an "Original" connector from MR. handsfree with charging capabilities but for now we have to DIY.
BTW. I tried to update my phone with the latest ROM and the sound was lost through the connector, so I am back to version 1.03.00.
Good luck with the project.