If you're not buying junk then you don't need service at all.
All the best Japanese high-end tonearm from the 70's/80's are just fine without any service, but you must buy a perfect sample from an audiophiles, not a hardly used broken or damaged items.
It's better to buy a NOS unit or a MINT condition sample.
I have many vintage tonearms in use, they are all perfect without service.
I would never buy any used tonearm with some defects related to bearings etc.
If the bearings are fine then all you need (maybe) is internal rewire, but even this is not always necessary!
All the best Japanese high-end tonearm from the 70's/80's are just fine without any service, but you must buy a perfect sample from an audiophiles, not a hardly used broken or damaged items.
It's better to buy a NOS unit or a MINT condition sample.
I have many vintage tonearms in use, they are all perfect without service.
I would never buy any used tonearm with some defects related to bearings etc.
If the bearings are fine then all you need (maybe) is internal rewire, but even this is not always necessary!