You should map out what you are going to write about in your body paragraphs (pre-writing, outline, four-square). What are the main points in each paragraph that could help you to form the statement? Once you have that, it should make writing the thesis statement a bit easier. If this is just a general overview, you could write something like, "Tchaikovsky's composition was shaped by many events that occurred early in life, during his adult life, and long after he passed away." Again, it would largely depend on what you want your reader to know about the paragraphs they are about to read.
Complete sentence. The comma is used the right way so it wouldnt be a comma splice, and if you replaced the comma with a period it would be wrong, so not a run on. That is why it is a complete sentence
