I have gone down this route. I have a restored Thorens TD124 and Garrard 301 rimless grease bearing. First, I echo Millercarbon and Chakster, though I lack the experience Chakster has with a wide range of arms. I have two Reed 3P's. There is nothing more important than an arm that is easy to set up. Reed supplies levers for each and every adjustment. Loosen a knob, adjust a lever, and bang, you're done. Reed has a unique design on the bearing assembly which is not quite a bearing assembly.
News flash-despite the success, the Fremer Video-which I own-is so basic that it is practically useless. Properly setting up a table is not like watching a Youtube video to learn how to replace a cartridge valve in a faucet. Getting azimuth, VTA and SRA optimized takes a ton of hands on experience and special tools. My advice is to hire a pro. That is what I do-Brian Walsh. If you buy a Rega or VPI Scout or similar, sure, that basics will do because you have a basic table. But if you are going to the lengths that you are going, don't waste that great deck and arm with a mediocre to bad set-up.
I have used Jim Campbell. He worked on my TD124 before many years later deciding to have it worked on again, this time by Greg Metz. He is a great guy. His forte', in my humble op, is building plinths. Do you want your Garrard cleaned up the proper way? I mean really cleaned up and restored? There is Ray Clark of Classic Turntable Co. in Wakefield, Jolly UK (I bought a bunch of aftermarket parts including his power supply and have talked to him) and there is Greg Metz of STS just outside Nashville. These two will strip your Garrard 301 down to the parts, if necessary sandblast your chassis and repaint it. These two know every trick there is to restore a Garrard to like-new condition and which after-market mods are worth the money and effort. Greg is an absolute technician and stickler for precision when it comes to working with turntable mechanisms and parts.
I don't want to take any business away from Jim Campbell, but most Garrard 301 experts will tell you that slate is not the best choice. Sure it sounds like a great idea, but that doesn't mean it is optimum. Steve Dobbins out of Boise Idaho is a noted Garrard 301 expert. He supplies a plinth known as the Dobbins Plinth. I used Russ Collinson, again in Jolly Old England, (Layers of Beauty) to build a huge custom Shindo-like plinth with Cocobolo veneer. If you go to Russ' website, you can find a video of him applying the veneer to MY plinth. Everyone who has seen it, including Brian Walsh, say they have never seen a nicer one. My point being that imho layers of proper wood are better for Garrard 301's than slate. The Garrard 301 needs to be tuned with complimentary sounding components, not deadened.