See if there are any Utube clips on how to do it if you think it's doable go for it if not then leave it be.I'm tempted but Ive never done a repair on this scale. Based on past experience on working on other engines, this would take me much longer than Id ever imagined. I also have this niggling fear that there may be something else wrong.
The nocco trickle chargers are pretty good. Ive rigged it up so the cable comes down from the ceiling and there is a permanent waterproof connection to the battery so you dont need to remove the seat etc. Its very easy to plug in after use.