You got some good responses and you are on the right track to begin with.
I drain the oil in my 203 car between the FSS intervals and use Mobil One and a new filter. After draining the oil from below and replacing the filter, I pour in eight quarts. You can get a special socket for the oil filter at your dealership for about $10.
Not having a dipstick drove me crazy at first, but it really is no problem. I'm sure you've figured out how to check the oil on a flat surface without the engine running. The dipstick can be purchased for service use, but it costs about $60. The computer gets the job done without having to open the hood or find a clean rag.
Hint: There are two belly pans under the engine. You only need to remove the rear one to access the drain plug.
Hint: I bought a magnetic drain plug and replaced the original with the magnetic plug the first time I drained the oil. That oil change was BEFORE I took it back to the dealer for the regularly scheduled FSS service.
I hope you enjoy your 203 as much as I'm enjoying mine. Did you get a manual transmission? I'm a manual lover, and the six speed is fabulous!
Have a great day,
Change oil hot and change oil often