I would be a bit leery using Lowe's. They simply will use an A/C company from your area, who has guaranteed Lowe's a pre-selected price to charge, and often will shortcut the installation to keep a profit margin. Contact your neighbors. Ask them who they used, and if they were happy with the results. Lastly, get 2-3 quotes, and make sure they check your duct work to determine if it contains asbestos, since many do.
My neighbor used a high priced A/C company 4 1/2 years ago and they charged him $12K for a full 5 ton A/C system. He said he went with them because they were the only company to offer a full 5 year warranty on everything. Well, 4 1/2 years later, his A/C system is broken. The company came out yesterday and told him that only his compressor has a 5 year warranty, and the rest of the system only has a 2 year warranty. They said he has a leak in the system, and this is not covered in the warranty. They charged him $300 for more freon, but will need to come out again in the next few weeks to determine where the leak is at, for an additional charge.
Bottom line, read the fine print.