Re: charging from ac power
The parts diagrams only show a simple non regulated rectifier. But it's a 4 wire type so presumably you have a 3 wire connection to the AC lighting socket.
There is a battery charging kit part no 0582105 which is essentially a rectifier with a mounting, wiring harness and fuse which plugs into the lighting socket. It's $78 US though.
The alternative is the fit the rectifier, terminal block, wiring and other minor bibs and bobs that would be fitted on an engine with battery charging as standard. The rectifier alone is $50 US, so still not a cheap project
If you are Ok with a bit of DIY electronics you could use 6 suitably rated diodes to make up a full wave 3 phase type rectifier. In which case the bottom diagram below will be self explanatory and tell you all you need to know. It is the cheap way of doing it.
If you are worried about lack of regulation you will either have to find a regulator rectifier that can be used in place of the normal one or fit an add on regulator. Given a good sized battery you should not need to worry about the lack of regulation, but don't run the instruments directly from the engine without the battery connected ..