I cant remember where the O tube is, If its like the intrigue its up under the brake res somewhere. Pull it and see if there's any junk in it. If the system has been open a long time I would just change everything and only flush the evaporator ( would be nice to change that too but who wants to pull the dash? and its much smaller than the condenser so it will clean up better). Theres ac mineral spirit flush kits you can buy.
When you say you have a vacuum pump I hope its not one of the air operated ones? If so those aren't really that good at pulling moisture out of the system. Yes it will work but the a/c as a whole will not last as long as doing it the proper way. Most PAG oils used in a lot of todays cars reacts with moisture and produces an acid that destroys the a/c system.
Depending on what you decide to change, make sure you replace the high/low valves. You may check the system for a vacuum leak but you most of the time you have gauges connected so the shraeders condition goes untested until after your done.
and compressor failure in the a/c industry we call it "black death". You can find a lot of information on google search with this term.
