2002 C230KM coupe

[EAL]

This is the second time the oil level message came on- first was right after a dealer service- took it right back, they said there was enough oil and 'probably' a bad sensor and gave me an estimate that is not in the budget-

Drove about a month, today warning again-- so most likely this sensor right?- any way to tell for sure, then order parts- and can someone with general/good mechanical skills do the job?
thank you.