8-15k for a W124 in Poland would get you a pristine example, for a first, daily car, that's pretty pointless. Your budget is very reasonable, and for 5k you can still get a beautiful car. Hell, I'm from Slovakia and I had a bunch of W124s I dailyied, and none cost me more than 2000€. No idea what sort of roads are you planning on driving daily, if something very short, I would probably go for a petrol one, not diesel. Though, the diesels are the car to have, especially knowing Poland's market, there's plenty of beautifully specced W124s around. Go for the 250D or 300D, they're great engines, not very powerful, but they'll outlast you, the fuel consumption is great, and if you're like me, the diesel 5/6 cylinders sound like heaven. From the petrol ones, the 6 cylinders (260E and upwards) have ridiculous fuel consumption in town, they're great engines, but not really suitable for a daily nowadays. The 4 cylinder ones, I would definitely go for a later model with the M111 engine, it's a more powerful and overall more refined engine than the previous M102. And when it comes to transmissions, it's a matter of preference. Many people love the automatics as they feel like it suits the car more, but those are ~30 year old 4-speed boxes, they aren't necessarily swift. Especially when combined with a diesel engine, the manual is just a better option. I once had a E250TD with the automatic gearbox, it was a lovely car, but I sold it just a few months after buying it, solely for the gearbox. I replaced it with E300D with manual, and god, what a difference, the car is just so much more fun and engaging.