Engine mounts are going to be most expensive at the GM dealer, because they buy them from Toyota, put them in an ACdelco box, and ship it to the dealers. Second most expensive Toyota dealer. Sometimes the national chain auto stores are more expensive than the Toyota dealer but not always. Least expensive will be online parts stores like Rockauto, they sell OEM quality products, but at a lower cost, because it doesn't have TOYOTA marked on the part.
If you tell us what engine, transmission, and if it's AWD or not, we can help you find the right engine mounts.
Here are some links for you to look at.
http://www.gmpartsdirect.com/" onclick="window.open(this.href);return false;
http://www.toyotapartscheap.com/" onclick="window.open(this.href);return false;
http://www.oreillyauto.com/" onclick="window.open(this.href);return false;
http://www.rockauto.com/" onclick="window.open(this.href);return false;
As for having them installed.
Motor mounts are one step up from doing brakes. Any shop that does any work on engines can perform this service. The GM dealer would likely be cheaper than Toyota because some Toyota service departments charge a premium to work on a "Non-Toyota" car. Call your dealers and get a quote.
Also, try calling around to other auto repair facility in your area, you'll be surprised how much the price can vary. Consider non-national chain stores, as they will normally have less overhead and better prices.
Ask for a quote on the labor cost, and how much they charge per hour.
There is a small, one man, auto repair shop near my house that does all the work on my Vibe. He does everything from oil changes and brakes to full engine replacement.
A job like this is the perfect opportunity to try a small business in your area. The recession killed off some small shops, but that means the good ones should still be around.
As for motor mount "upgrades" there is only one. Polyurethane engine mount inserts. These fill the empty area around the rubber mount with Polyurethane. They make it so the engine doesn't move around as much under hard acceleration and braking. They also make it pretty unbearable at idle. I had these mounts installed last spring before the autocross season started, then had them uninstalled as soon as the autocross season was done. Poly engine mounts should really only be used for race cars.
Here is a link to the ones I have.
http://www.monkeywrenchracing.com/produ ... cts_id=482" onclick="window.open(this.href);return false;