Goalless draw wouldn't be too bad for either side. Olympiakos would have had a clean sheet at home, Chelsea would have an away leg passed. Of course, it is possible that we would be knocked out because Oly would get a result at The Bridge, but in games like these you can take nothing for granted anyway.
As for squad selection I would say so:
Čech, Belletti, Carvalho, Makelele, Essien, J. Cole and Drogba should all start.
Elswhere there are options. Terry/Alex - I would prefer Brazilian. Terry made several mistakes (one of them costed us goal) against Huddersfield and he doesn't have enough match practice. Ballack/Lampard - very much the same situation here. Lampard recently recovered from his injury and Ballack was rested at weekend. Also he looks to be better suited for European game, he can hold the ball and he is bigger threat from set-pieces than Lamps. A. Cole/Bridge - depends purely on tactics. Bridge provides better support for attacks, but defensively Cole edges him and I think we should go for safety first option here. Malouda/Kalou/SWP - the most difficult choice here. Malouda is the most experienced and he is also the player of the highest quality, but he cannot run at the defences and he is the weakest of the three when he is isolated against his defender. Kalou is terrible finisher, but he is commited, he has trickery and he can cause all sorts of problems for defenders. SWP is extremely inconsistent. He would be more than capable to destroy any oposition on his day, but these "his days" are few and far between. His crossing ability is terrible, his passes and shots aren't good either. And by selecting him you would force J. Cole to play out of position. Given that, I'd choose Kalou, who also could provide the best support to a lone striker by getting into opposition's penalty area.