Any laser type printer uses the same principles and processes you've pointed out. That in turn applies to all such "laser" printers with minor acceptations and even those really aren't that different, just the build-up. The only so-called laser printers are LED type that displace actual laser beam. Everything else follows the same pattern though other than what's needed for LED use. the mechanics are basically the same.
As the problems you've described, here "cleaning" is clearly needed. Any decent tech would have done this or at least look to see if that was required. As for vacuum cleaner, here you better decide that the vacuum cleaner you use is capable because vacuuming "toner" is a destructive process and should any of that get into eletrical paths, shorts will be coming. Not only that but such fine powder tends to wear down any bearings, etc.. Toner type vacuum cleaners aren't made to be the best out there, they have a short wear&tear period, maybe 50-100 cleaning then poof something is bound to happen.
My trusty HP Laserjet 2100, which I bought "as is" at a thrift store five years ago for around $10, started printing very faintly after the first couple of inches on the page. Tried a new cartridge (remanufactured) and had same problem.
Finally discovered a page -- http://www.printertechs.com/printer-troubleshooting/13-cleaning-laser-scanner -- that suggested cleaning the transfer roller, which "pulls" toner off the print roller onto the paper. I took it out, vacuumed lightly with the brush attachment of a portable vac, and put it back. Printing now is excellent.
This advice also might work for Laserjet 6 and Laserjet 6mp, which are very similar to the 2100 (and one of which I also have).
I buy remanufactured cartridges on eBay for both printers for around $12 each and they usually work fine. (I got a bad one from one vendor, and they replaced it ASAP with no arguments). Quality of photos and graphics is not that great, with visible flaws quite common, but for general home use this has gotta be the cheapest printing there is.Of course, you can also buy a factory HP cartridge for around $120 (not a typo).
These old HP printers are what helped to give that company its once-great reputation. I'll keep 'em going as long as I can. On the other hand, I wouldn't buy a NEW HP printer for any reason, especially the inkjet models -- I've had too many unhappy experiences with them.
BTW, if your Laserjet starts having trouble feeding paper from the paper tray to the print mechanism, there are repair kits on eBay for about $12 (and which fixed the problem completely). Search for "roller repair kit" for your model.