Vintage Cars: 1979 Mercedes 450sl, oil pressure guage, fuel delivery system


Question
I just received my mom's "baby" that was sitting in her driveway for 5 years. She said it would start right up...it didn't. The good news....it was her baby & looks great, it only has 84K miles on a 30 yr old car & I now have it running! Bad news is it runs very hot, it starts right up...when it wants! My question is, after a car sits that long...what should I have checked and/or replaced. I'm not REAL familiar with the terms the mechanic told me he did but I heard transmission seals replaced, alternator, something about timing...he said I would have no problems...I had to get new battery the next day.
What could be the cause of the intermittent starting, especially with a new battery? And do they all run really hot? Is there any solution to cool it down? Also, the oil gauge goes to the top when gas pedal is pushed but lowers to middle when idling??!!
I'm so excited to own this car and want to make sure I treat it right.
Thank you so much for any input you can provide.

Answer
Congrats on a great car I have a 72, and have owned all sorts of MB's
These cars run hot but should not go over 175F. sitting is not good for a car, especially this one.  Gas tends to gel , so your hard starting could be anywhere in the fuel delivery system, from tank to pump to lines to the injectors. MY guess without more details is injectors, but all the fuel lines and filters should be flushed and filters  changed. The Oil pressure guage is acting correctly , it should peak under load, settle in the middle for idle
If you need to communicate with me feel free to use this email , its quicker and I can supply all sorts of information should you need it  -  fhfarm@gmx.com
Good luck and happy motoring
ron