does Jeep Liberty ('05) factory stereo have preamp outputs

No. None of MOPAR is radios have them. But you can always pull it out to be sure. Its very easy - just pull the dash ring out (its on snap links) and remove the 4 screws that hold the radio in place.

no it does not ,they only have an aux plug socket for the cd multi changer,and if u wish to use this for anything else u will need a special lead & adaptor as they have a thing called canbus wireing simply means that most of the do more than one function which wakes it very dificult to do any thing else with the electrics or radio u could change the head unit but u will then need a face plate to fit as radio an odd size l know kenwood do one for this jeep but it is not cheap the plug & adaptor is about £60 & the face plate £50 if u dont have the limited version u could try & get the whole set up from one as they have a premium sound package that has an amp as well