I used to be a Hindu, hell I technically still am, since I believe in the sanctity of the Vedas.
Then be a Hindu if you still consider yourself as one - if you want, that is. If not, there's a Seekers DIR you can use.
But something always bugged me, it always seemed so very Indian, that I never really felt at home, there would be mantras done in hindi that I thought were sanskrit, which lead to a lot of frustration.
It can be very difficult to remove the religion and culture from one another, look at Islam and Arabic - most Muslims believe you should only perform salat in Arabic.
The reason mantras may be done in Hindi instead is because Sanskrit is not commonly spoken and is a language with many grammatical rules like Latin, whereas Hindi is an easier language. Not to mention, you would be able to learn Hindi at the same time.
Truthfully, Hindi should be a non-issue, as long as you are taking spiritual fulfilment from the place. If you aren't, then what is the point? Find another mandir to worship in, if that is the case.
Also another question, I always had trouble with puja, it never really felt structured, is there a bit of a guide? (I learnt as best I could about Hinduism, but without help, you kind of get overwhelmed)
That is kind of one of the things I like about puja. Depending on what you would like to do, there are various styles. Since I'm a recent adherent, I'm still practising a basic form of puja, lighting a candle and incense stick and a mantra, etc.
Wikipedia has things you can do (under "Offerings") in the
Hindu puja section.
You can also read this for puja to Ganesha:
A Ganesha Puja
Just do what you think is right, and then you can solidify it. Or, you can seek a guru who may teach you a way to do it that is most appropriate for you.
Also would the gods accept alcohol? I always felt kind of strange if I tried giving them alcohol.
I wouldn't give the gods alcohol, but I do not think that one should consume intoxicants anyway. Offering something that causes carelessness, has health problems associated with it, and what is physically addictive to the Divine seems rather disrespectful, if anything.
Some people may do so, though, but I've not encountered them personally and so I would steer clear of it if I were you - it may be done in a long, elaborate ritual, or some form of Tantric practice, but if you don't know what they are or how to do them, I'd not really give them booze as an offering, lol. Instead, give milk and water to God.
My $0.02.