Yes, stainless steel will be fine. Polythene, ceramic, enamel or glass is also good, but probably best avoid non-stainless steel or aluminium as acidic things attack them (to tell stainless from aluminium try scratching it -- aluminium is much softer than a steel knife).
Once you've put the culture in, keep it warm, either in the airing cupboard, or by wrapping something insulating around it. Close any vents the pan lid has.