I do not see any difficult open questions here - it is a main field of CheckPoint in production to connect the companies main site to worldwide distributed remote sites using S2S VPN and nearly every customer i do know of uses that functionality. All is throughly documented, see CP_R80.10_SitetoSiteVPN_AdminGuide for details. As long as no 3rd Party GW is involved, configuration is straight-forward after some basic decisions have been made. In sk105119: Best Practices - VPN Performance you can find general performance guidelines for working with VPN.
Shortly on the question details: Using Domain based VPN is compulsory, and the open ports required are taken care of by CP implied rules; object definition in Dashboard is very easy, of course the public IP of the remote GW has to be the main address used (and part of the VPN domain). And yes, you shall establish SIC as suggested in the CP manuals and guides .
CCSE CCTE CCSM SMB Specialist