Per: with the SJA1000 you still need a 82C251.

About the learning curve:
if you have a CAN-Serial or CAN-USB device with a simple software plus for exp. an EVA-Kit (SJA1000 or T89C51CC01 based) you will be able to send / receive messages in a very short time, perhaps in half a day to a day after studying the registers etc. Perhaps its best to start both without interrupts. (Sometimes the examples that are included in starter kits are much too complicated.) You could end up using just this for your simple application.
Total Time a couple of hours to a couple of days should be enough.

For starters I would recommend:
- use Std Ids (11bit)
- avoid remote frames
- get familiar with the CAN frame (exp 11bit ID, Data Length Code (0..8) DATA[0..7])
- read some articles on higher level protocols, (in Europe CANopen is the most accepted protocol) especially how they use the identifiers. (In some of my projects I stick only to the CANopen addressing of its PDOs which I use for everything plus I use the SYNC Object, so my application will not disturb the use of CANopen based addons, sensors, etc)

good luck

Werner

PS. the 80C390 *IS* a powerful chip with many non standard registers / features / startup behaviour, but in the end the CAN part is pretty straight forward. It took me about a day to switch from C515C to the C390.

PPS. an oscilloscope is nice to have. Try sending a message to the bus without another node, or take away the resistors on the twisted pair an look what happens.