sealing the grout

How much should it cost to have someone do sealing of the grout. I would say the entire tile area
is probably 1100 sq ft. Since it is only 3 months old not much cleaning or removal of stains.
Also can someone recommend a good contactor for this. Called one of the numbers listed
in builder's recommended list. Got a quote for 850/-. Does it sound reasonable.

Sounds kind of pricey.  Is this not a DIY project?

This would be a rather easy DIY project, just get a good sealant from Miracle sealants, like 511 Grout Sealer and apply as directed.  Most of these are roll/brush on, wait, the wipe off.  None of these require any specialized tooling for sealing grout, tile or stone.  The sealants are expensive though, a quart could easily be in the 40-60 range depending on the sealant, I think my gallon sealer was well over $100.