Nicholas - I would suggest you find a local garden center who has on staff a landscape design person.  Often they can come out or look at pictures and help you select what you like for specific locations.  Or they may be able to recommend a local landscape company that you could work with.

It appears that you understand how planning and site assessment are critical to having a beautiful end result.  Remember, gardening is a process and you can make it more manageable by working on specific areas in stages.  At the garden center, browse the plants and trees to get an idea of what you like and that will help the designer include your picks in the plan.  And, be sure to tell the designer how much time and money you wish to invest in this garden so it fits your needs.

Also, I am including a link below to a wonderful MSU web site that has a wealth of information about gardening including shrubs, lawn, vegetables. etc.  

https://www.canr.msu.edu/home_gardening/

I hope that helps!

I forgot to answer your question about poison ivy.  The first step is to identify it and once you do that, carefully eradicate it.  
See more details in the article below.

https://www.canr.msu.edu/pestid/uploads/files/PoisonIvy_E3438_AA+(002).pdf