There are maybe 30 Torx screws to remove to take apart the preselector. There's a number pattern for removal and reinstallation screws (like an engine head). If you don't do it in the right order, you can warp the cover.
In the past, I've used a q-tip to dislodge the whiskers and an air compressor to blow out the remnants. If you want to go to the extreme, you can mask off the edges, back out the tuning slugs, and hit it with a clear coat to keep them from growing again. I've done that with GE Mastr II preselectors before.
If I may make a recommendation, I'd replace all the electrolytic capacitors on the uniboard. They always leak and can cause trace damage. I keep a bag of tantalum caps just for that purpose. There's also 2 large caps that go bad on the control board. Change those, too.
The VCOs are the 2 metal boxes in the top left and right (TX and RX) above the uniboard in the drawer. The intermediate power amp is between them. They have an RCA jack and a 5-pin molex connector tied to them. I've had to short the laser-etched tuning strips to bring them down to lock in the ham band before. They do not have a tuning slug like the UHF/800/900 models. The frequency tuning is not done with the VCOs anyway. It's done on the uniboard via a tuning slug on the 14.4 MHz crystal package. There will be a hole in the top of the metal lid of the drawer marked as the frequency adjustment. Use a plastic tool, otherwise the metal in the tool will throw off the tuning and it'll take 3x as long to set it.
If you're interested, I may have a high power amp from a high-band PURC station available for purchase. It'll plug right in to the MSF. Let me know and I'll see if I can dig it out of storage.