welcome to the forum!
Is there a way to tell if its been grafted?
in the original picture you posted, a few inches up from the soil, you can see where it look like one tree (darker green, upper) was inserted into another tree (lower green, base). for many people, this would be the first issue where a decision would need to be made before any other decisions could be made. you have many options, here are a few:
1) you can try to grow the trunk thick enough so that the graft will disappear. This occurs in landscape specimens (because the trunk is allowed to grow without constraints), but in bonsai it is certainly harder to accomplish, and would take decades if it were to occur at all.
2) air layer above the graft - perhaps just a few inches above the graft where the interesting movement in the trunk begins. this would normally be done if your goal was to create a bonsai with the specific cultivar you purchased. in your case, the cultivar is unknown (it may or may not be among those for which there is a general consensus regarding their suitability for bonsai. some japanese maples, like bloodgood or red sentinel, are considerably less suitable).
3) ignore the graft totally (knowing that this will never be an exhibit-level specimen) and simply have fun and practice with this tree
If you choose to air layer (at the appropriate time of year), i would not repot this tree (since you want vigorous roots, which will not be part of your future tree anyways)
if you choose to ignore the graft and create the best bonsai this tree can be, i would repot and explore the roots at the appropriate time of year - i would do this in-person with somebody more experienced for the sake learning about repotting as well as everything else the conversation will inevitably lead to.
@LanceMac10 posted some photos and info here that might be helpful to you:
I'm hoping the long title of this thread will help others in my situation find this thread in the future. From what I have been able to find, the information on this is scattered here and there, and it is even often unclear what species people are discussing. I spent the last two days reading...
www.bonsainut.com
other options exists, but these are probably the most common
yesterday i posted some links in 2 posts in the following thread, and these may also be helpful to yo if you have not already come across them:
Hello, I am new to Bonsai and have been doing a ton of research and have gathered my materials and have even shaped a couple of small beginner trees. My question is about my Japanese maple I was gifted. I need help getting the trunk to thicken and establishing a strong nebari. I got over zealous...
www.bonsainut.com
there are some great clubs, professionals, and bonsai-specific nurseries in your area of north america - these are all great places to learn and access bonsai material
