I have 299,300k on my car. The only failure has been the fuel pump, and that was at 287k, and it was the original. I am making the second trip to Atlanta in three weeks with this car so I can break 300k before I do my swap. There is nothing wrong with the motor I am swapping, I just want more. So if you only have 170k, just keep your maintenance up, you should have a good car for quite some time. Plus with 170k you won't get jack on a trade in anyway, so replacement value is more than cash value.

UIM. Upper Intake Manifold.

The UIM and lower intake manifold (LIM) gaskets are common failure points on the L36 (Series II 3800) engines.

Keep going and if it ain't broke don't fix it.
Unless of course you will sleep better at night.
Continue with regular maint and suggestions posted.