The OVP is a $50-70 part through Fastlane at the top of the page, and is easy to replace yourself - it just unplugs! It is a surge suppressor for your car's computers and electronics. I would read about OVP in the archives / search, and have it checked at the dealership to make sure, but your car seems to have the same symptoms as many others in the past.
Regarding the expense to maintain, while there are certainly lemons out there for every car ever made, I have found my 300E to be more reliable and MUCH less expensive to repair than my Acura Legend. Good luck
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E