Shops makea large cut of their money on parts. They charge full retail and get them for about 40% off, nothing wrong with that, its part of running a business. They also have to make money on their hourly rate since most are not "book rate" shops anymore. Yes, your bigger dealerships are, but smaller shops usually are an hourly pay scale. They have to pay everything from facilty to wages from that $90/hr they charge.
Myself, I would rather do the work myself and have a greater sence of pride in my car and knowing that I didnt skimp on the repairs. About 90% or car maint & repairs can be done easily at home. As far as tools, you can never have to many, if you need it, buy it, then you have it for future use. If you dont want to do that, rent it from the part stores & let them store them.
As far as shops installing customer parts, thats touchy. Alot of people want to have a shop install used or super cheap parts. Then they complain about the shop when the part fails and wont do free repairs. With Lil Red (1987 Porsche 924s) I have found 2 local shops for future repairs.
Shop 1 - Has a 2 price labor system. Pay by check, credit/debit card you pay standard labor. Pay CASH, its about 1/2 to 2/3 of the standard rate. He will install any part, but will not stand behind those parts, only his labor.
SHOP 2 - A standard repair shop with standard rates, all the techs are factory certified and very up to dateon European cars. He will let you supply your own part, the same quality as his or better & no used unless its no longer available through retail. Again, he wont stand behind your parts, but only his work if you supply parts. If you buy his parts, no worries at all.
I would much rather do my own work. Its not that hard if you take your time and its rewarding in more than the just the cash saved. You respect your car more and in turn you take better care of it.