I've found the following series of youtube videos very helpful in giving a high level 101 on getting started w/ Bonsai. Just learning some of the vocab, a bit of the process, and mainly what search terms to use has been very helpful to learn more from the bnut forum. The deciduous videos would be helpful for you with this tree (there's one specifically on cleaning up a deciduous tree), then you can drill down into species-specific care & tendencies.
I've read in a few places Japanese maples bleed excessively in the spring if you prune. If this is relevant to your species, you'd be targeting next fall after leaf drop for pruning, which gives you even MORE time to decide