New Member - 2007 Civic Si Modification Order

Hello All Civic Enthusiasts,
I have a stock 2007 Si with 220k on the K20. The car runs really well and is in good shape, but I hear pinging going up hills at times doing about 45mph. I'm thinking if I need valve adjustment. I do know I need a new knock sensor. The local shop I take it to told me I also need a new exhaust system. I'm overseas in Germany and I need to order what I need. I was thinking about installing some headers. Basically if you all could tell me everything I need to order for the headers/exhaust system, that would be a great help to me. I just don't have lots of time to research it all myself. Should I rebuild the engine before doing mods? If I do mods, what order should I do the mods.

Thanks for answering my questions and appreciate your time to answer my questions.