I did not see any reason in your post to think your engine needs rebuilding.
You state that its "noisey". The noise should be addressed. Do you feel it is engine bearings? The M110 has fairly noisy valve mechanism. If its excessive you might want to fix the cause; a bad cam or rocker arm.
You state that it uses too much fuel. That is very unlikely to be a mechanical issue. Do you know that your compression is poor? The running should be addressed by a competent tech before you decide to keep it 10 years. My wife drove a 1981 280SEL for 14 years and it got about 21 mpg on the highway at 80.
Bosch Master, ASE Master, L1
33 years MB technician