Assuming it was a CD rip to .mp3 then yes, you can just change it to .flac probably.
But the problem comes when its an .mp3 that was not ripped properly(?) and/or downloaded from bizzare sites, and of course; how many kbps it has isnt indicative of the record quality at all, badly sounding songs exist in all formats.
Getting a hold of really good quality songs is easy as long as you share tastes with a lot of people or if the album is easy to get for a decent price. For people that listen to outsider-ish things its a whole different story unfortunately, i was glad to even find the songs i had before, albums would have cost me nearly a fortune probably if i had wanted to order them from somewhere, theyre not on itunes and some of them were hard to get as crappy .mp3's, let alone a good .mp3 or .flac.
Supporting artists is good and all as long as you (the consumer) dont get dragged along the pavement for it...(money-wise)