Cylinder numbers are as viewed looking forward. The rear cylinders are odd numbered and the front even numbered. No 1 is rear at twelve o'clock as Aerials suggests. A handy mnemonic for identifying which magnetos serve which cylinder spark plugs is: Right (5 letters) = Front plugs (5 letters again) and Left (four letters) = Rear plugs (four letters).
I agree with Avionic Type about the 1830 being (relatively) easy to work on (as is the DC3 airframe although rigging the ailerons can be time consuming as there are no control stops - the ranges are governed by cable adjustment).
I'm not a lover of the R2800 though.