well after much stuffing about and being stuffed about i have some upgrade brakes for my beast. scored some fg xr6t front brakes, these are the 322mm jobs as opposed to the 298mm stock ones i currently have. im kind of average on the spanner action, so thought id get a professional to install them for me. had 2 quotes and 2 wildly different prices. both say its best to drain and flush the whole brake system during install for best results. one mechanics place says $350. the second said $450 cash and he keeps my old brake setup. im just wondering whats actually involved here and what i should expect to pay? i was thinking it would be about $150 to $200 plus brake fluid???

350? man ill do it for a carton

just take wheel off, take brake caliper off ( 2 bolts )
undo rake line (1 bolt)
take brake caliper bracket off (another 2 bolt)
slide disk off ( nothing to undo as they are floating disks)

install is opposite.

got new brake lines with the brakes, so will be putting those on aswell. dont i need to bleed the brakes to avoid air bubbles in the system?

yes if you remove the line from the caliper youll have to bleed the brakes

If you were in Brisvegas I'd do this for you no problem for a quarter of one of those quotes. Get yourself some tools and do this yourself, you'll save a fortune and learn something. All the advice is here on the site anyhow.