I'm guessing that "new BP series 1" really means "new-to-you BP series 1" or you might not be asking this question. Do, by all means, let the sound bother your. Fixing the problem before spindle bearings are damaged may save you a bunch of money.
Get one of the downloadable copies of the manual and look at a head diagram. There are lots of bearings (moreso in the VS head), and you can use your knowledge of where they are located to listen while someone else makes the cut to see if the noise is likely bearing related and if so, which bearings. I have a cheapy HF "stethoscope" that has a solid rod for input. It is designed for listening to engine noises and comes in pretty handy for locating the source of bearing noise. You may want to pick one of these up if you don't have one.
The answer to your original question is that the quality of the bearings depends on their location. All of the head bearings except the spindle bearings are pretty typically a typical quality radial ball bearing and in my experience, were not proprietary. The spindle bearings are ABEC 7 from the factory and are a radial contact thrust bearing pair. They are proprietary and have a center race ground offset from the outer race such that a pair of differential inner and outer spacers define the preload.
You can do a search here on Bridgeport spindle (here) and find a post from a while back where this was hashed out. If you need spindle bearings, don't let someone sell you a standard bearing pair based on the first 5 or so numbers/letters in the part designation. The extra numbers/letters in their designation defines some pretty important specifics that make them cost a lot...and work correctly They define the proprietary differences (like differential race heights) etc.
Do read up on head lubrication. The spindle bearings do get oil in a cup on the head and *nothing* in the head is lubricated by your one-shot oiler. That handles oiling way surfaces and cross-feed nuts only.
Often, the original oil lubed spindle bearings have been replaced with sealed, grease packed bearings that not only do not need oil in the cup, but may have their grease washed out by thin spindle oil. The only way to know is to remove the quill "cap" and look to see if you see balls on the other side of the shield/washer. If you see a typical plastic bearing grease seal, they are newer, sealed bearings.
Ease of replacement depends entirely on which bearings you end up having to replace. The spindle bearing set itself can be removed without major head disassembly. These are the most expensive bearings, however. Great care needs to be exercised in bearing removal after you get the spindle out of the quill and you may want to read up on spindle repair. The spindle pair has to go back in correct back-to-back orientation, too.
The other bearings in the head require more disassembly, but are far less costly.