Believe it or not, I was at a friends house, and had to do some work, and was impressed by the wrenches he had (a flex head ratchiting combo wrench) - fit and finsh nearly at the Snap-on level - say slightly better than Matco. I aked him where he got them. LOWES house brand!! Went out and bought a few (I must own 5-6 7/16, 1/2 and 9/16 wrenches - at least those 3 in every toolbox)
RE worn out old nuts/bolts etc. Something I learned way too late (like near the time I stopped messing with cars), I don't deal with old worn out bolts etc. If I'm doing a project, part of the budget is "New hardware". Say I'm doing drum brakes - not only will I buy new pads, but I figure every other time or so, the cylinders, adjusters, hoses, etc will get replaced (or overhauled at worst) - hardware goes in a parts cleaner, gets wire brushed, inspected, and if questionable, replaced
Doesn't hurt that Dad was a HVAC mechanic and collected more hardware than you can shake a stick at, and when I sorted it all, I made a list of "what is low" - and when I have to place an order with MSC/ENCO/McMaster etc, I'll pad out the order to either the minimum/free shipping/etc amounts by looking at the list and saying "Oh, throw in a box of N sized hardware"
I probably own a greater selection of 1/4" and down hardware than the average well stocked hardware store - stainless, Black Oxide, various lengths, head styles etc. Can't tell you how many times a neighbor will come over on a Sunday, hand me a screw, and say "you have something like this?" - I'd say 70% of the time I have an exact replacement, and another 20% I might have "well, I don't have it in bright steel, but I have it in oxide" Or "I don't have slot head, but I do have phillips (or hex or torx)", and I ask how many is in the set, and we replace them ALL, so they all match (reminds me, I have to order another box of stainless socket head cap screws)
One REALLY smart thing to do, if you do any mechanical work (and if you have some room on the boat) - go out and buy some "hardware assortments" - don't go for those ones "in the bins" the advertize in the backs of magazines - usually low quality and the "wrong stuff". Go to a place like MSC or McMaster, and order stuff
Start with catalog page
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1791and work through pages in that area - say pages 2000 through 2009
If you want better grade, buy the American brands - Holochrome etc (usually not available in the assortment)
Another good source I found, but it's been years since I bought - every once in a while, back when ebay was small enough that you could actually look through ever listing in hardware every day, I'd find someone selling "drops" Hardware that was accidently dropped on the floor at some big plant or hardware Mfg. It actually doesn't pay for them to sit down and sort them, so they will get thrown in big mixed bins and sold - I was buying what would have been mil-spec stainless hardware, 1/4" and down by the pound, I think I bought 5-6 lbs. I spend a lot of time when I had time to kill sorting the hardware - I'd walk around with a bunch of zip lock bags, and "gee, I have to wait for the MD, lets sort some screws" etc
Another good one - if you know a good mechanic who travels the road - see if hell let you raid his "Hell Box". Usually a box of misc hardware, screws, everything, that he tends to pick up. They tend to just throw spares in there. One of my chores when Dad was working was to (every couple of months) Sort the box, and put things away "Misc 3/8" bolts", Misc fuses, Wire Nuts, etc etc
Another one - I rarely throw out mechanical "stuff" without stripping it. I can't tell you how many bearings from hard drives (GOOD Magnets), small screws etc I've gotten that way