John,
You don't indicate where you are, so the market may be quite different than I am used to. 10K will net you a cherry 560 in the SE with 100+/- kmiles. You have to buy with your head, and not let your heart get the best of you.
154K is not tooooooo many miles, but be advised, any 560 is at least 18 years old. Rubber, fabric, mechanical joints, hoses, electrical wiring all are getting tired by this time. Pay particular to service history on the fuel system and timing gear/chain/guides. The climate control systems are noted for potential problems, especially the vacuum pods used to handle the air.
The 560, and other benzes, take off in second gear unless nailed at WOT. Tranny's are not noted for being problematic, but search and you can find posts on adjusting the harshness of the 2-3 shift-point via the modulator.
Oh, on the climate system... These units were reported to be marginal at best when new... Don't expect too much in hot, humid climates.
Best news is that near 100% of anything ever needed is still available, and most even from the dealer. Many other speciality shops offer OEM and repro parts reasonably, but I recommend a deep pocket book or a lot of DIY accumen... Not a lot of dealer knowledge on these old dogs out there, and service can nickle and dime you to death otherwise (especially diagnosing the fuel system and climate control system).
For what it's worth, look at
www.oursl.com and see what they have available in the cars for sale listings... this may give you an idea of value. also, if you subscribe, they will send you a "boot camp" buyers' guide to the 560 and links to many articles are there.
good luck, and happy hunting.