Your 309 will replay Music Just Fine and it will sit well on your TT.
As a design of Tonearm, I feel I am safe to say the 309 is
approx 25 years Old or is using Technology from Brand Siblings of that age or older.
At present you are looking into having it Serviced.
This as an idea can easily escalate into Considering having it Modernised because of the age of the design.
The idea of a Modernising if adopted will usually lead into the investigation of exchanges of the original Bearing Parts and replacing these with the latest equivalents.
Note: Micro Bearings are not produced solely for Tonearms,
they are commonly used as parts in Dental Equipment, where multi thousand revolutions are carried out in Short Bursts.
Tonearm Manufacturers adopt these parts to be used, hence the discussions to be found about about how these Bearings are best prepared to be used on a Tonearm.
As it can be found certain individuals believe the design of the Bearing needs secondary treatments to get them to their optimum for a Tonearms Function.
Today there are philosophies for Tonearm Designs that will be more focused on how to get the best from the mechanical interfaces for the parts used.
A common first step is to focus on the Micro Bearings, with a intention to reduce friction when in use.
As said some are known to carry out secondary treatments to a Micro Bearing, i.e,
flush the Bearing of any lubricant as the lubricant in use can cause a Friction if the lubricant has not got a very Low Coefficient of Friction.
Running the Bearing Dry will not necessary improve on the
Coefficient of Friction,
but there are reports that there are audible differences to be picked up on through doing this as a procedure and this has made this method grow in popular use.
Introducing Ceramic Bearings for their Low Coefficient of Friction is another measure adopted and the same again with the removal of any lubricant.
Additionally the Bearings Designs over time have increased their quantity of Ball Bearings, so exchanging a Older Design Bearing for a New Increased Number of Rollers in a Design has been seen as a upgrade,
as the Increased Number of Rollers will decrease surface area contact between each Rollers, hence to be seen as a Method to decrease Friction.
Running these Bearings flushed of lubricant will also be a method,
where the fundamental behind the Bearing Exchange and Removal of Lubricant is to decrease friction at the mechanical interfaces within the Tonearm.
Today there are purpose produced synthetic lubricants available,
that are of the Lowest Coefficient of Friction known.
These are industry specific and not easy to source from a common search method, knowing the name of the Substance is critical.
When a Lowest Coefficient Lubricant is used, it will surpass the performance Manufacturers Lubricant used on their Micro Bearings when the Bearing is to be used on a Tonearm,
the Lowest Coefficient Lubricant will prove much more beneficial to the Bearings Performance,
when added to a Micro Bearing that has had the Manufacturers Lubricant Flushed, against the option of running it dry.
If a modernising the Tonearm develops into having a focus on the on how to best treat the Bearing and Selecting a Internal Wiring that will be capable of creating the minimum of resistance when interfacing with the Tonearm.
When these considerations are combined and put into the Tonearm,
they will further the Design for a improved Tonearm that will not have been put into use by the Manufacturer on many if not all of their models.
The above are focused on the Mechanical Interfaces Only.
There are the Limitations of a Design through the chosen Geometry,
and the stability of other material choices, as these will have to have the utmost consideration for their suitability for the chosen usage and their reaction to being in the environment.
There is no point having a Part that is part of a Interface where a freedom of movement is critical, and the Part Absorbs Moisture in a Environment that is Humid, or shrinks when exposed to a certain temperature.
There are also in use to date Updated Methods,to Improve on Wand Damping, due to modern materials and there availability for usage.
My take on the OP's original question, is to enjoy the New Acquired 309.
It will replay music and should make the New Owner more than happy with the way it performs.
If the OP wants to go down any route for seeking a improvement,
from a Service, or extend to a Modernisation, then before monies are spent, a understanding of what might be needing to be discussed will be a good Corner Stone to start the inquiries.
