What the valve cover page actually says
The symptom list names a cracked or warped cover and a failing built-in PCV, also called the CCV. The FAQ on that page says that if the plastic cover is warped or cracked, or the built-in crankcase vent has failed, the whole cover gets replaced. Ask any shop whether its quote is gasket-only or a full cover, because that is the biggest reason quotes differ. See Valve Cover / Valve Cover Gasket.
We do not have a separate priced PCV valve. Do not compare a loose "PCV valve" price from another brand with these cover quotes.
Smoke, smell and misfires
Owners describe a burning oil smell and smoke from the exhaust-manifold side, oil seeping around the cover edge, and oil in the spark plug wells with misfires. Oil in the wells is a reason to look at the cover before replacing coils. Other misfire causes are in the BMW Rough Idle and Misfire: Causes and Repair Costs. A rattle on acceleration with codes such as 2A82 is the BMW VANOS Solenoid Symptoms and Replacement, not a failed cover.
Which engines, and which warranty notes
The page covers the N52 and N51, the N20, and the N54 and N55, on the E90, E92, F30, F31, E70, F15, F10 and E60. N51 SULEV owners report both the cover and the gaskets replaced under the SULEV emissions warranty. On the N20 and N26, a BimmerFest note says the N26 valve cover gasket is covered for 15 years or 150,000 miles in PZEV states. Check the warranty before paying. The engine pages are BMW N52 engine, BMW N55 engine and BMW N20 engine.
Book time cited for an N55 cover is about 5 hours, and one dealer billed 6.8. On the N20 the job is longer because the intake-side parts, injector harness and vacuum lines come off.
The B58 cover is a different part
The B58 plastic valve cover has its own page. Its symptoms are a burning oil smell, smoke from the exhaust side, seepage at the cover edge, and oil in the plug wells. That page does not call the failure a PCV valve. The cover is replaced as an assembly and the injectors come out, so labor hours spread from the reports on that page. Some B58 cars may be covered by a campaign, so check by VIN. See B58 Valve Cover Replacement and the BMW Oil and Coolant Mixing at the Filter Housing for the other B58 leak, which is coolant from the oil filter housing.