Need Some help guys

It would help to know what kind of trains you have - Lionel O-27? American Flyer S? HO? N? Guessing from your description it sounds like you may have an HO set with plastic snap-in trucks and truck mounted "horn-hook" couplers, and these trucks are prone to falls off and these couplers to break. Replacements are available. You need to decide whether you want to restore the set as it was, or upgrade it, and if the upgrade how much you want to spend - more common train set cars sell for just a buck or two at shows, while quality replacement trucks and couplers can add up to over $6 to 8 (in HO). What is your skill level? Upgrading could involve plugging the old truck mounting holes in the car bottom, drilling new holes to take new truck mounting screws, and building up plastic mounting pads at the ends of the cars to allow body-mounting new replacement couplers. GQ

I do have HO scale train, I am pretty handy with tools and modeling, but if there is an easy way to put on couplers and wheels that are durable I would prefer that route, but whatever you think would be the most durable and best running, I always hate the de-railing of a model train, I will appreciate any help you could give me thanks very much,
Steve

Then stay away from those all-in-one wheel-and-coupler setups. They pull OK, but tend to derail when pushed, especially in curves. Those cheapy Talgo trucks also have a lot more drag on the axles than some of the better ones. Kind of like pulling a train with the brakes on.
If they're old Tyco or Bachmann cars and locomotive, scrap them and start with at least Athearn cars/locos or something nicer (read: more expensive/better detailed). This doesn't have to be done all at once.
Athearn cars can be improved by using Proto 2000 or Intermountain wheels, but this is not strictly necessary. Athearn wheels are almost always good right out of the box.
If you have brass track, dump it (eventually) and go with nickel-silver. Reason: brass oxides don't conduct, nickel-silver oxides will, plus silver rail looks better than gold rail.
Good trackwork (tight joints, rails in gauge) is probably the single biggest preventive measure you can take for derailments. Quality equipment would be second. Even Intermountain cars won't run well on lousy track.
Model Railroader said it some time back and I agree. To paraphrase: fewer derailments means more enjoyment of the hobby. I think we can all agree on that.
Jay CNS&M North Shore Line - "First and fastest"

expensive/better IYO: Who makes the best, highest-quality HO cars and locos? The stuff at my local mostly looks like crap.

If you mean the best for a starter trainset, I'd say Athearn "old style" locos and either Athearn or MDC cars.
If you mean best styrene kits, I'd say P2K, Intermountain, and Red Caboose cars, with P2K locos.
If you mean the best of the best, then you're talking resin kits like Westerfield, Sunshine, and Funaro's newer work, or brass. Genesis or brass locos.
YMMV
Brian

Locos: Standard Athearn and P1K/ P2K are best in the "usually under $50 category". Some of the Proto 1000/2000 models retail for more than that, but can be gotten for less through flea markets, swap meets, and internet sellers (beware of shipping rates, though). All around best I've found are Stewart for Alco models. I don't own any Atlas or Athearn Genesis, so I can't comment on those, but general consensus around here seems to say they're worth the price.
For good-running cars under $20, Athearn is good, although some complain about the liberty they've taken with the door measurements to make able to open and close. I also have one Accurail car. It runs well enough, but being molded in color and not painted, it looks sort of cheesy. MDC/Roundhouse kits are also good in the under $20 category. The problem with these kits is you can often spend $5-10 per car to bring them up to snuff (better wheels, Kadee couplers & details). I usually just upgrade the wheels & couplers, shave the grab irons and replace them with .020" brass. I skip the stirrup steps for now. My main complaint with Athearn is that they're too light. That's easily solved with lead weight compliments of local tire shops. After all, if the cars came at weight, Athearn'd have to pay shipping on that dead weight, and we'd have to pay for it also in the price.
Those P2K cars are sure nice, but that detail stuff may get broken if you don't handle it carefully. They sure are pretty, though. Eventually for me. I have to rebuild my fleet first.
Jay CNS&M North Shore Line - "First and fastest"