Early 2008 Macbook (4,1) maximum RAM per port

I have an early 2008 macbook white 2.4Ghz, or the macbook 4,1 and I understand that the maximum RAM that this model will support is 4GB.

It used to have 2x2GB RAM running on it but recently one of the slots stopped working and the computer wouldn't boot unless I took the RAM out of the slot. That leaves my computer running on just 1x2GB RAM.

The computer has been very slow since then and I was wondering if I could install 1x4GB RAM in the remaining working slot, will it make my system any quicker? Also, if I were to replace the hard disk with a SSD, would it be faster as well?

Where can I find the maximum capacity of each RAM slot?

Thanks in advance.