Wow, that thing is in nice shape for 9 years old. I feel bad now. My poor 'ol Deere GT235 garden tractor looks nowhere near as nice as your machine. Of course, I have a rough yard and I make that thing work...
I had an LT2000 with the same engine for a couple years until I got the John Deere 425. It was a bit small for our 2 acres, but it got the job done. That Kohler always ran great. Now the mother-in-law has it and it's still working great for her. Not sure what the difference is between the LT1000 and the LT2000 though. They appear to be the exact same tractor, except for the color. I ran Rotella T6 with an FL-910S in it.