Go for it!
I just paid $10,200 for a bone stock 2000 7.3 with 214,000 miles on the clock. It took me a long time to search out an Ex that hadn't been destroyed by a generation of kids & pets or modded out to the point of destruction. This one had impeccable maintenance records and two separate shops I had inspect it gave it a 9/10 overall condition. If you've found a lower mileage, unmolested Ex for 12K & change - my advice would be to grab it up as it may be awhile before you see another one. As far as efficiency an reliability go; spend the $$ to replace every drop of fluid with high quality synthetics, replace the trans cooler with an OEM from a 6.0 & add some good gauges to keep an eye on everything. I called the guys at DP tuners, said I was getting 16-17 on the highway and wanted to know if I could bump up the mileage without increasing performance. Their advice was to leave it alone, take good care of it & enjoy another 200,000 miles. By then it'll be paid for & my next call to DP will be about an extremely sick Ex! Good Luck!