As far as matching the paint, most parts suppliers (NOT autozoo or pupboys type stores, the real folks who supply the garages and such) that do autobody and paint supplies may have a scanner to 'read' the paint and spit out a mix code ( for me, it is the local UAP / Napa store ).
They claim this can compensate for age and fade.
Just make the area you want checked as good as possible, to get as close a match as possible. Buff, claybar, whatever.

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1984 300 D runs, interior
1984 300 D light hit in front, RUST, mint/perfect dash, decent interior (see above), parts car
(hate to kill one)
1998 Dodge diesel