At 10 years it may have three year old tires... are you going to replace them? $4000 installed. Complete oil service at SpeedCo... $300. Replace serpentine belt... $150 side radiator, $250 rear. Replace air dryer... $250. Replace shocks at $200 each X 4 or 8. That comes to $6000+/- installed. Not sure how you could spend $10K having someone else doing the work on a 10 year old DP.
In my situation at 10 years I had 6 new tires and two 3 years old. The 6 cost me $3000. I do my own oil changes... $150. The serpentine belt ($45) has already been replaced and the air dryer at 8 years ($75). At 65K miles I see no reason to replace the 10 shocks... rig handles great. My cost at 10 years... $3200 + $250 ($3450) as I also replaced both engine batteries that were 10 years old and still going strong... used them in a machine I own. Brake cost on a DP with exhaust brake is not a issue.
Would you buy a rig from me? Probably not as the records I have are written on the filters or some only in my memory. Serpentine belt was replace at aprox 6 years and when it breaks I'll put the old one on (side radiator) until I can buy a new one.