The general rule is that you select a notary, not the seller, so you should be able to shop around and find the notary that will answer your questions. There is also a 'permanence' in Geneva http://www.notaires-geneve.ch/permanence.php
where you can get to meet a notary and get some basic advice for a small sum (similar to 'permanence juridique' for legal advice).
It may also not be a bad idea to contact this company (already recommended at the forum): http://www.d-l.ch/
. They can read the contract for you and give you useful advice on a range of real estate issues.
Finally, if you are buying 'sur plan', it is worthwhile to check the area (for environmental information, noise level, status of project, other development projects in the area). The site in Geneva where you can find all kind of useful information is http://etat.geneve.ch/topoweb4/Main.aspx