Yes I play both as much as I can.
I believe the middle C on guitar is the 2nd string 1st fret, but the 5th string 3rd fret matches the middle C on piano.
Maintain a guitar by playing it and changing the strings out once the become dark grey/charred color. Never rest the neck of the guitar on anything except its strings to prevent warping/buzz.
They are quite unique instruments so it takes time to be proficient in both.