Don't know the Author, Help...

I became an avid sci-fi reader my sophomore year in high school. My school library had a fair collection but since I was not buying books back then I was a bit lax in recalling book names and their authors. That came later. Anyway, I returned to my old high school almost 20 years later in order to maybe find these books and I discovered that they redesigned the library and many books were gone. There are two books that elude me to this day and I'm hoping someone will be able to help me, or at least enable me to find them.

These two books were written prior to 1982. It's possible maybe even in that year, but I doubt it.

Book #1: Author's last name starts with a W I believe and maybe ends with -ski. The book was about Mars and a lost/abandoned civilization. I can't recall all the finer points of the plot but the original inhabitants of Mars went exploring the universe and basically mothballed their planet for their eventual return. While they were gone they came across a paranoid race that later turned up in our solar system and was secretly manipulating Earth. I want to say the main character's name was Jim, but I could be wrong on that. Anyway the book ends by Jim traveling with the returned Martians to earth to help prevent some sort of catastrophe and Earth responds to them with a space fleet to defend Earth. The Martians pull some type of trick and the Earth force retreats. Jim was initially ashamed at his planet's response but the Martians assure him that they were quite brave.

Book #2: Mankind has gone out into space and has met many new races among the stars. At some point a alien space intelligence becomes a threat to Earth or something and in order to possibly communicate with this alien intelligence a single man is chosen to visit 3 known alien races for physical and mental modifications that take the man further from his humanity. The story is about how he changes and how people treat him as he makes this sacrifice in order to save mankind. The book ends with him making contact with this alien intelligence and of course it's a she and he manages to avert the disaster.

If anyone can help me determine either the author's name of either two books or titles, I can then find the book and see if it's the one(s) from my high school days.

Also if anyone else has a memory of a book but can't quite recall the name or author I'd be more than willing to try my memory and maybe assist them.

Thanks....
Talos