I'm replacing the chain ring on an old Trek 1200...probably from around 1990. I had the chain ring replaced a few years back at a used bike shop and I think I got an obscure part. There are two front rings with 52 and 42 teeth and 7 rings on the cassette. I'm planning on replacing it (the front rings not the cassette) as the teeth are worn down, but I'm worried I'm going to replace it with some chain ring that is somehow incompatible with my gear system. Any tips?

Thanks!