I'm assuming the gunshop near you charges $200 plus parts? Or what handguard and gas block are they installing? Pulling a gas block then installing a new handguard isn't a big job, half hour or less really unless the original barrel nut is totally stuck - so $200 in labor is way too high. Alternatively, if the $200 includes parts and labor both, it must be a pretty cheap handguard they're using, and a non-adjustable gas block.
For my AR's (a whole bunch of them), and any I build for others (a whole bunch more), I use free floating handguards, and more importantly, adjustable gas blocks to give me ultimate control over the action. In general, I expect to pay $75-100 for the gas block alone, plus $150-250 on the free float handguards. So $50-100 in labor, $75-100 for an AGB, and $150-250 in free float handguard, $200 isn't enough for quality parts, if the parts are included, and it's FAR too much if the parts are not included.
How much a non-floating handguard will affect your shooting will depend on how variant your positions might be. If you're shooting free recoil from the bench, and ONLY such, then a free float guard won't make much difference. If you're shooting from a fence post some days, sticks another, the hood of the truck another, a bipod, a bench, a sling... Then a free float tube can make a huge difference in POI consistency. I have 2 remaining rifles which run clamshells, one an M4gery which I won't ever update, leaving it true to form, but I don't often shoot that one, and the other is a rifle I'm holding effectively on pawn - if I end up keeping it, it'll either get sold or get a new handguard and gas block.
