Anything else I need to watch out for beside the wiki guide there?
Yes, if you are in the US, you must have an EPA 608 certification to do any type of work on a refrigeration system. If you get caught working without one, you can get large fines. Also, depending on the state you live in, you may also need additional licensing or certification.
Why do you feel like you need to run a vacuum on your system? You don't run a vacuum on a charged system (contains refrigerant) because the vacuum will remove the refrigerant. So yes, you will loose all your refrigerant.
I just fully recharged it last month
Who charged the system? Yourself or a technician?
You would first recover any refrigerant left in the system (you cannot release the refrigerant to the atmosphere it is illegal to do so) this can be done with a vacuum and recovery tank.
Now that the system is empty, you can proceed with replacing the needed components or test for/repair leaks (you can use a special dye and special equipment that detects the dye / you could charge your system with nitrogen to leak test, this is what we use, there are other ways you could leak detect.
After any work is done, you can then evacuate (vacuum) the system. This needs to be done to remove all air, moisture, and all gasses from the system before charging with refrigerant again. Air, moisture and gasses other than the refrigerant, can cause high head pressure, cause acid to form which is bad for the components, or cause sludge to form which is also bad among other things.
Once you are done evacuating, you add the proper refrigerant type and amount.
I ask again, why are you putting a vacuum on your system?
There are many things that can go wrong, the big thing is bodily harm. Refrigerant is EXTREMELY cold and will burn your skin including your eyes.
The fact that you are asking these questions shows you don't have the knowledge or experience to service a HVAC system.. This is not a homeowner DIY project.