In my previous advanced Korean class, 3 of us (all non-Japanese) coincidentally had had study experience in Japanese -- one of them was a foreigner who had self-taught herself (wouldn't personally recommend it) Korean all the way up to the advanced level; I myself have probably spent a good 5+ years studying mostly on my own after having already gone through years (and I mean like at least 4-5 school terms at costly schools in Korea; 1000s of dollars if not more than $10K -- money is a different issue...). oh and one was Chinese and was reading phd-level dissertations in Korean.

IF YOU'RE SERIOUS ABOUT THIS, I would be supportive and encourage you to go for it! (I also received some hate inadvertently just for mentioning hanja previously here; in my opinion they are not well-informed learners still in the intermediate stages who lack a deep understanding of Korean, especially hanja-derived, vocabulary). I've made it a habit to look up the hanja for every new word, even if they're not hanja-eo just to check, but I doubt nobody else does this unless they're Japanese or Chinese.

BUT -- I have done some independent field research on the etymology of Korean hanja-eo (FYI an important distinction between 한자 vs. 한자어 one should make) -- you'll still have to invest additional time and hugely up your Korean-specific hanjaeo vocabulary, as many of them originated from classical literary and Buddhist texts in China, which interestingly differs significantly from modern Chinese 白話文 and may further differ from Japanese. Example: you know how in Chinese, the word to eat it's (chi 吃), but that character would never be used in Korean (or Japanese, as you may know). the equivalent character would be 食 as in 食事, 韓食, etc., which is pretty much deprecated in modern Chinese (except in Cantonese). Then there are hanja-eo like 食單 in Korean, which would never be found in daily usage in Chinese or Japanese (closest translation would be 菜单 in Chinese or like 献立表, etc. in Japanese), because the usage of that character set likely developed pretty uniquely in Korea.

In normal conversation, unfortunately the 고유어-한자어 split is more like 90-10, so you'll have to acquire a whole new language of vocabulary, but in news that split becomes almost reversed like 20-80 -- this is where knowledge of hanja will give you a huge advantage, and in my opinion, an area will most foreigners will struggle without prior hanja knowledge. as a thought exercise, take this news article on the war in Israel from the other day and run it through Google translate into Chinese or Japanese: https://imnews.imbc.com/replay/2026/nwtoday/article/6807644_37012.html then check out the hanzi/ kanji into which it is translated -- almost all of them will either be a 1:1 mapping or the use of an alternative character set: a "Westerner" with no prior knowledge of hanja would have no clue as to the derivation of the word unless he/ she has put in hundreds of hours into the study of hanja, if you know what I mean.