Outside temp & oil press guage

Good morning all! My first post and I sure could use some help. Since buying my 2000 CLK430 I have had a couple of problems arise.
 
1.) Oil pressure guage is very very slow to rise, but does reach approx 80-90 psi after about 1 minute or running time. No knocks from the engine so far. I''d like to know where the oil send is and how hard is it to replace.
 
2.) My outside ambient temp guage is currently stuck on 136 degrees. No movement from it in the last week of driving. Where is the senser located and how hard is it to replace?
 
Thanks for the help folks.
 
Regards,
Mark