It's a gorgeous specimen and not at all "overgrown" - that's exactly what a low graft weeping dissectum should look like.

I wouldn't do any obvious pruning on it but the canopy could probably use some thinning and removal of dead wood. Wait until all the leaves fall first.....and you might need to help raking them gently out of the canopy with your fingers - they often get caught up in that nest of overlapping stems.

Then first remove all the dead wood - it should be obvious, as a lighter colored gray compared to the normal darker twig color. Once you've removed all the accumulation of dead wood, you may find the canopy already much lighter and thinner. But if you wish thin further, you can selectively remove branches that may overlap too thickly, bend oddly, are congested, etc. You may wish to come back to the forum at that time with clear photos of the leafless tree and we can direct you further.

As to being able to see the trunk and bark........that may not be as easily accomplished with this specimen as with some others. Because this is a low graft, non-staked tree and with a weeping canopy that reaches almost to the ground, the trunk is never going to be hugely obvious, even without leaves. And you want avoid at all costs trimming off the bottom of the branches to raise the canopy significantly. That results in a sheared off, Dutch boy haircut look that destroys the natural aesthetic of the tree.

But do come back to the forum with clear photos of the tree without its leaves. The exact situation and growth habit of the tree will be much clearer then and we can make additional pruning suggestions at that time.

Thank you!

I have a question though: over the past few winters, we have had huge amounts of snow almost immediately after the leaves fall. The snow sticks around until April (at least!) and there is hardly any time between the leaf fall and new leaf formation without being covered in feet of snow. If I decide to prune, WHEN?

Also, help me understand the difference between thinning and pruning? I understand removing dead wood and have tried to do that, but it is challenging when the tree is so big and I can't get around it fully!

I agree it's gorgeous and I'm not looking for a manicured look (for lack of a better term), just don't want to neglect the tree.

To add further to what Gardengal said, prune from the bottom up and the inside out. Crawl in up under it and start taking the dead growth off. Then by observing what died and why (shade) remove what's going to die of shade on the inside in the future. Remember, you're still inside the maple.

Here's an example of what I'm doing with one of mine. Notice down in the back the branches are congested. That area needs to be thinned...The inside ones first and work out and up until the desired density of the canopy is reached. Do not open the trunk to too much sun from the south. The canopy should be umbrella shaped with a loosely scalloped look rather than even all around.

Here's that picture. Looking west. This was grafted down low also.