Question: If I do not really believe in Pure Land, can I still practise, just in case, and succeed in going there?
Answer: True practice is with all Three Provisions (Faith, Aspiration and Practice) as listed at http://purelanders.com/2015/12/30/%E5%BE%80%E7%94%9F%E5%87%80%E5%9C%9F%E4%B8%89%E8%B5%84%E7%B2%AE-the-three-provisions-for-rebirth-in-pure-land The first is Faith, which is crucial. It will be cultivated if you keep learning systematically and comprehensively via classes while practising. It is alright to be healthily skeptical if there is clarification of doubts.
Without Faith, there will be no Aspiration for actual Practice. For example, if there is no confidence (i.e. Faith) that there is a wonderful sale happening at a certain place, there will be no urge (i.e. Aspiration) to go there, what more proper journeying (i.e. Practice) to reach there. Even if there is some travelling, it is probably half-hearted, with tendency to give up at any time. In terms of reaching Pure Land, half-heartedness means there is attachment to elsewhere (e.g. Samsara) which holds one back. This is why we should cultivate wholeheartedness with the Three Provisions.