To oil the marker, drip a few drops of oil in the macro, air the marker and shoot about 20-30 shots. This will cycle oil through all the vital parts of the marker. To lube your ram, you will need to remove it from the marker. Take off the back plate, and use either a ram removal tool or a pair of needle nose pliars to unscrew the ram. Once the ram is removed, apply light grease to the o-rings. Lithium grease is okay, but it's got petroleum in it, so remember, it will have a higher tendency to dry up, swell o-rings, etc,. I'm going to start using Super Lube myself, it's entirely synthetic with PTFE particles suspended, should be great for all paintball applications (
http://www.super-lube.com/cgi-bin/miva?Merchant2/merchant.mv+Screen=CTGY&Store_Code=SL&Category_Code=SG). You could lightly grease the ram shaft (the rod the hammer is attached to), but don't overdo it, as aged grease turns to sludge and will slow your ram up and it'll need replacing sooner.