Got some finger use back
I have no idea your familiarity with firearms & cleaning of them, so I'll kinda get wordy here...
Ok, if yours is the Four-Screw type, where you have to undo 4 screw to release the action parts from the housing,
you'll be looking for a 99-series manual. But because the 60 & 99 were Tube-Fed models & the 989 is a Box Mag fed...
there are some minor differences.
The 989 was made from 1962-1966 and was
based on the same action as the Old Model 60 & 99 series.
The 989-M2 was made from 1966-1979 and the action was upgraded to resolve certain minor headaches that appeared
in the previous design, along with a more M-1-like stock.
All you really need to do to give it a good military field-strip cleaning...
First remove the action from the housing via the 4 screws, and set it aside...
then remove the bolt & bolt handle, followed by the recoil spring & recoil spring guide.
That is ALL the action you want to take apart the first time...this is a learning situation & basic cleaning.
You can get more intense after you feel you know it better...kind of like breaking in a new girlfriend
Take a toothbrush & some patches & your favorite gun cleaner...and CLEAN the action carefully, but completely.
Try not to monkey about with the E-clips...but if you knock one off & loose it,
Ace Hardware & other Hardware stores carry 'em.
The rails on top where the bolt rides usually need some serious cleaning...baked-on gunpowder residue...etc...
I usually take the time to hand-polish them...as it helps the bolt to ride better.
The bolt I usually hand-polish as well, using Arkansas Stones, but sandpaper on a flat surface works too.
Polished bolt & rails = easy sliding

Hit the inside of the action with sandpaper...it'll smooth it up as well.
Check the plastic doodad on the back, that's the buffer...if it has cracks that go all the way thru, it needs replacing.
If not, leave it be for now, but order a replacement, you'll need it, as it IS an OLD rifle.
Clean the Recoil Spring Guide until it's SMOOTH as a baby's buttocks. Any roughness
J&P springs makes a great spring kit that interchanges from the model 60...hammer & recoil springs, you'll probably need those eventually too.
I change out the buffer & springs with any used semi-auto rifle I buy that's over 20 years old...PM is helpful

(Preventative Maintenance)
But the first time is a serious cleaning ONLY...it's a learning of the overview of the systems.
Then I go out & shoot it...if problems occur, I come back to the table.
CCI Minimags are great first-time ammo.
You usually don't have to worry about quality with 'em, they just shoot consistantly.
When you put the action back into the stock, screw the stock screws in to Finger-Tight...then work the action a few times.
It should feel smooth & right, then use a half-turn on each screw, then check again.
Once it goes to feeling Hard & not smooth, back off a quarter-turn, and check until it feels smooth.
This gives you proper screw tightness, you'll figure out the exact spot with time.
Mag Cleaning...the bottom plate on the mag slides off, but the first time you may need to give it some help...
Take a bore brush (9mm works well) and scrub the inside of the mags...clean the springs & follower...
run a oil patch & then dry patches thru em, then reassemble. You want it oiled, but not sloppy, if ya get my drift.
When cleaning the Barrel & Chamber, make sure that when you are done, you get ALL the Oil out of the Chamber & barrel!!
Use dry patches & q-tips if you have to, but get that chamber totally free of oil!!
When you fire a semi-auto, if you have oil in the chamber it will quickly combine with the burnt gunpowder & create a gummy substance...
which means it won't extract very well before long...even though everything else looks fine (extractors/ejectors).
I think that's everything important...Eli will probably be along shortly to correct anything I've missed