Hey, better a stale thread than stale bread!
I will say that yes, If you have just a modicum of mechanical ability, you can take this on. The 5000 series in general is really Free Spool Baitcaster 101. There have been more than a few baitcasters on the market which were uh-oh specials as soon as the right side cover was removed, but the Ambassadeur is not one of those. The most frequent mistake made upon reassembly is incorrectly positioning the anti-reverse dog, and sometimes the pinion gear. Over-oiling and greasing are popular, as is thinking that WD-40 is a good bearing lubricant...over time, WD will turn gummy, which is a good thing to remember about door hinges also.
If you can take good close-up digital photos as you disassemble the reel, it is a good idea to do so. Use a good clean, well-lit work area, and use a system for grouping your parts. On a right retrieve reel, I always started by removing the left side cover, and then the spool from the frame. Then you can go to the right sideand remove the right casing by loosening the big thumbscrews to free it from the frame. Now you canlay the gear case on its side with the handle and star drag up. Now you're in position to remove the right side cover, which is done by removing the handle nut, handle, and star drag (you may need to grip the shaft flats gently and firmly with something non-marking to unscrew the drag star). Remove the two screws remaining on the cover, and you're ready to remove the cover.
You may need to use a thumbnail to gently pry the gear plate and the cover apart as you jiggle them slightly, and this should be done slowly and gently, but firmly to remove only the sidecover, with its right side spool bearing cap still attached. As you lift, be sure you're not lifting the gearshaft, spacers, and drag washers along with the cover, and be sure that the anti-reverse dog remains in place also on its shaft, just forward of the free spool button.
This gets your side covers, spool, frame, and gear plate apart with all gears attatched and in place, and if you take your time, the rest of the procedure is pretty straight. As you reassemble, do not grease the nylon levelwind timing gears, or any part of the levelwind: Just lightly oil. Know that the spool edges are toleranced to the frame, and that the frame is not a bearing surface: Keep this tolerance clean and dry, and your levelwind and pawl area clean and oiled, with a drop of oil on your bearings, andy your reel will always cast well.
Yes, I used to do reel repair! I still have my first Ambassadeur, a new 1962 model that my Dad gave me for my 11th birthday. I hope this gets you started on the right foot!
Dean