If you look up in right top corner of this page, you will see a search block. It's just to right of HFE. Just type in "Garrard SL72" or "Garrard SL" and all sorts of threads will come up. with specialized info that you may find helpful. Check topic list in Garrard forum for topics related to your unit.
Also, Garrard SL72B manual comes up here: http://www.vinylengine.com/library/garrard/sl-72b.shtml
Should help you get started. You will need to go underneath and remove all the old grease which is referred to as Garrard Gorilla Snot. I replace it with automotive wheel bearing grease, but there are others who use white lithium grease or other similar greases. Also, you will need to put a drop of 3 in 1 electric motor oil in the top motor bearing, just under pulley, and you will have to take bottom off motor and clean out bottom bearing and lubricate it with the same oil. You may want to clean and lubricate the ball bearing that lies under the turntable to quiet it down, and clean and lubricate the cam gear that is turned and moves the changer mechanism. All this stuff should be done, and if you take your time and work carefully, you will have a good result.
You will need to check idler wheel to be sure that it is smooth and round, with no dents or gouges, and that rubber has not hardened or gotten slippery. If you disassemble, do it carefully, and record it by taking pictures. be careful of C-clips and clamps on ends of shafts. DON'T just do guesswork, or you won't be able to get it back together again. The longer you take to do the work, the more difficult it will be to remember how to put the thing back together again.
And good luck from that slippery, greasy old guy, who doesn't remember how anything goes together,