The earlier 530 and 730 (50s and 60s) Records have fewer plastic gears than the later versions. It's hard to say anything specific on a particular machine, but I generally take a chance on a vintage Bernina after a light inspection and if it looks nice. The paint on them is rather delicate, wear and use will show on these. I allow a few signs of age and wear, brownish staning will come off with a bit of cleaning and polishing.
For the internal plastic gears; they usually last decades, quite a few of the early Records still run fine with their original gears. That said, the nylon gear that turns the cam stack have cracked in some cases, the drive belts can need replacement. Theres probably two or three plastic gears in all. If a 530 is generally in good shape is generally worthy service and repair. These are probably my favorite zigzaggers, narrow freearm, runs light and easy, the CB hook and race give very even stitching, and good satin stitching. If the accessories still are with the machine, a fix up machine is often a bargain even after service and repair expenses.
There is one plastic gear turning the cam stack (under the top cover). There are one or two nylon gears in the freearm, the top of it comes off and there is a spring action part under the bobbin cover to relese it, rememer to take the needle and presser foot out to prevent scratching when you lift it off.
If the machine turns and stitches smoothly it is probably fine, but it's hard to tell until the machine is cleaned and oiled and you have had a chance to inspect it further.