Not only a case of miles, they pass the test of time as well...mine runs like it doesn't have close to HALF the miles it actually does...starts everyday, in the 100s in the dog days of summer and in the -20s in the dead of winter .just goes to show what a good engine the 3800 is.
But you having a 99, that car has ALOT left in it. But with 160k, it depends on when the previous owner changed the LIM & UIM gaskets and such but KEEP AN EYE ON YOUR COOLANT LEVEL!!!! That is of utmost importance! But it looks like Bill already has you on the right path for that! Other than that, just do normal maintinance and make sure your trans fluid is nice cherry red like cough syrup and doesn't smell burnt, and you have yourself a good car to mod and "jazz up"
But one thing we love here are pics...so if you have a digital camera, we would LOVE to see this SSE.