AliExpress had some shimadzu compatible septa, guess I’ll find out in a few weeks how good they are.

Also ordered some GC syringes, no clue what typical injection volumes are, so I just got a 10uL and a 100uL one wich should cover most ranges

Time to take apart the split / splitless injector and see what condition it is in. Make sure you are wearing gloves for this step, as any volatile contaminants will end up in your sample!

Luckily the instructions are very detailed on not only how to swap septum and liner, but also on how to clean them.
Nowadays most GCs use disposable parts, to minimise downtime and to ensure a lower, more reliable baseline even with very sensitive detectors.

These replacement parts can get pretty pricy tho, especially for hobby use so I am very glad this is possible. I will probably have to get more septa at some point, as they do have a limited lifespan but that's a problem for another day.

I wasn't able to capture it, but the liner is pretty filthy with burned bits stuck all over it, so cleaning it will definitely be a thing I do at some point.

The manual also seems to mention a different type of liner with what looks like a hole in the side. I am worried that that might be required for split injection, and I can only use this one for splitless operation, but I am not sure about that.

Liners are not that expensive at 25€ a piece but I only found them in a 5 pack so I'll probably pass on that for now

I managed to get a mostly complete scan of the manual here:
http://www.quimica.uns.edu.ar/images/stories/descargas/Manuales%20LIUC/Shimadtzu%20CG.pdf

Shimadzu seems to only sell the paper version for 65€ so this will have to do for now.

The unit is equipped with the following options:

TCD thermal conductivity detector
This seems to come standard with all shimadzu GCs, at least these old ones. In the diagrams it seems to only be used with packed columns, and requires a second, flow-rate matched stream of carrier gas for a comparative thermal conductivity measurement. As I only have the capillary column and FID is superior in most applications I don't think I will be using it, but I guess it is nice to have?
As a TCD does not destroy the sample it would be neat to first run it through the TCD and then the FID, but that would probably negatively affect separation, I don't think I've ever seen it done.

FID flame ionisation detector
FID seems to be the most common detector even on more modern units, so that is what I will probably be working with the most. It works by burning the sample in a hydrogen flame, this creates charged ions if certain atoms, like carbon, are present and these charged ions are captured and their current is measured. As these are extremely small currents modern detectors probably have a much higher sensitivity than this one.
It also requires more process gasses, where TCD only need the carrier gas FID also needs hydrogen and compressed air to work.

SPL Split/Splitless injector
This injector is used for the capillary column and resembles injectors common on more modern GCs. The sample is injected through the rubber septum into a glas tube called the liner where it evaporates. Carrier gas is decided into three ports. A small amount is flowed upwards as a septum purge, preventing contaminates and air from getting in if the septa develops a small leak. The main gas flow is directed through the vaporised sample and into the column and split line. The split line acts to dilute the sample in order not to overload the column. The ratio of gas going into the column to gas exiting through the split line can be controlled between 1/20 and 1/200, or splitting can be completely disabled. There is also a solenoid on the split line to save on carrier gas when no sample is currently being injected as the split flow is much higher than the purge flow and the column flow.
Note that this device does not measure split flow so you need to use an external flow meter to set your split flow rate, or just set it to something and never touch it I guess?

2 Port injector
These injectors are mainly used with packed columns, which I do not have. They are very simple with just a carrier gas line pushing all of the sample into the column.
Honestly I don't yet quite understand what the purpose of having two ports is, maybe it is just to increase capacity by running two columns at once?

Printables seems to have some RBF stands, yay! One less part I need to model

Let's give these a try:
https://www.printables.com/model/1076-round-bottom-flask-stand/files