You need to prime any repairs before painting with the oil based topcoat. Oil based paints can be used over acrylic or oil based primers. It's probably going to be hard to touch up oil based finishes because of the yellowing that occurs over time, you may need to actually paint entire pieces of trim up to a mitre. You can use the latex topcoats but again...oil based paint looks different and it gets yellow eventually, so if you have both in the same room, it will likely not look the same.

Thanks so much, paintguy. I'm sort of tempted to go with the latex because I've found a color that's a great match for the already-yellowed oil-based paint. So it's good to know I can use latex over primer.

My biggest problem seems to be getting the spackle right - it's hard to get those big chips completely level.

What I do is lay the spackle on pretty heavy over the chip and then after it's dry, I sand it down to try and match best the profile of the wood. I use lightweight spackle or lightweight drywall mud when I do this because I want it to sand easily....some of that wood filler or vinyl spackling doesn't sand well so it is not a good idea to use this technique with those products.

Great advice - thanks.