Hi,
If you decide to go the drill holes and lube route as a first step then lube it with ATF in my experience that is the best oil for lubricating fan bearings. WD40 is not a suitable lubricant for anything more than a day or so. WD40 is great at chasing moisture off plugs etc but not long term lubrication. Art Benstein has done the definitive text with EXCELLENT photos on how to do the complete strip out repair. The drill the hole is a good option to try, although if you want the certainty of knowing it is fixed Art's repair is the way to go.

Worth checking it is not just leaves but from what you say it sounds like the fan on the casing as shown in the photos I mentioned above. Bottom line is, the job as documented by Art is an easy job just very time consuming if you are not into car DIY like I am.
Cheers,
Checkpoint Charlie

Here is a link to Art Benstein's excellent site on how to do the fan motor. This was on an 84 so there are probably some differences.

http://www.cleanflametrap.com/

I am not a good primary source for this subject, having never done it, but I recall there were some photos and excellent instructions, I believe posted last summer. Lame a suggestion as it is, you may need to search the archives. I do believe your car is still built around that fan. And I do recall a post where someone drilled a hole near the motor and squirted some lubricant into it. Another possibility for the noise is something like a leaf or similar got in there, like cards on a bicycle wheel, and the click changes with the change in fan speed. You might try blowing it out. I get good velocity out of my shop vacuum for things like that. If that fails, you can always take the dash apart - the article I referred you to had the car down to the firewall.