short answer that is typed out EVERY WEEK HERE. ...there are no real good pre-assembled ones,
(oddball racing ones are EXPENSIVE).
get a local shop or parts dealer to use their BIG spring compressor on your OEM springs. or borrow theirs.
if you OEM spings have 200,000 miles or 2 much rust on them buy more. if not just keep using them.
but KYB struts and mounting kits are the things to buy, (mounting kits,...sometimes what you got is fine to re-use).
what I have done with my 2 cars: bought 4 KYB stuts online, from amazon / rockauto. and hand a local shop use spring compressors. on my particular cars all the mounts were still fine with 100,000 and 120,000 miles at change time. (the price on KYB mounts was the same online and local if I needed to buy them on install day).