Dead trees are dangerous for several reasons. They are structurally compromised and prone to branch or trunk failure, which can pose a significant safety risk to people, vehicles, and nearby structures. Dead trees can also harbor pests like termites, which may spread to other trees or your home. If a tree died from a disease, it could spread the illness to healthy trees. Additionally, the dry wood is highly flammable, increasing fire risk.

It depends. Smaller, younger trees take longer to mature, but they're more resilient, their roots don't get as damaged during transplanting, and they recover faster. Plus, they're much more affordable to plant, and it's possible to DIY the planting. 

On the other hand, mature trees produce fruit faster and provide more shade and privacy immediately. Ideally, a small or medium tree is the better choice if you can wait a few years for it to mature. But if you need immediate maturity, a larger tree is the only option.

Ideally, you’ll have a good enough relationship with your neighbors that you can kindly mention this task in regular conversation. However, every neighbor (and neighborhood) is different. Your best bet will always be to ask directly and nicely, offering to contribute to the tree trimming efforts if you’d like. However, if you are bothered by the tree and your neighbor is unwilling to cut it, you can involve the help of the homeowners’ association or local authorities, if applicable.

Tree trimming can count as landscaping, depending on how a landscaping business describes its services. Professional tree trimmers are more specialized than landscapers and offer trimming services separately from general landscaping.

When general landscaping companies offer tree trimming, look up the details. They usually mean shaping or seasonal trimming of ornamental trees, which is different from trimming larger trees for health or safety reasons. When possible, look for a licensed expert that specializes in trees and tree health.