In case you have still time to consider options you could search ebay.com for these modules "rf oscillator voltage controlled"
They come in different frequency ranges.
Using such a module, a mixer, a band pass filter at the high if frequency, a second module and mixer for the down conversion to the low if where you have the resolution filters, your most difficult components become the high if filter and the resolution filter(s)
For the log power detector you can use a AD8307 module, also from ebay
The log power detector doubles as a generic rf power meter that you can use, together with one of the vco modules, to test your if filter.
You can use a 4 opamp ic and some potmeters and other passive components to build a voltage sweeper where you have one potmeter for the center frequency and one for the span.
In this way you can build an sa without microcontroller, using a xy scope for display, and I know it will work as I did build it.