Unfortunately, I don't think the guy you talked to either understood what you were asking or has a clue what he's talking about. Of course it could be both. The 476 (not sure about a 476A) is the remote used with some Automate systems. Automate is essentially the OEM brand name DEI uses for some of their systems. The shop I worked at put numerous Automate systems in cars for dealers that the customers requested keyless entry in but were not equipped with it from the factory. If you have a Chrysler OEM keyless in your car I honestly don't see that remote programming in. And if that keyless entry in the Explorer was done by the dealer it's more than likely a Code Alarm unit that I'll guarantee won't be controlled by the DEI remote.
A $70 remote start add-on to a keyless entry system would scare the crap out of me. Quite honestly, I'd start searching for a different shop. Most keyless entry systems don't even have an aux output to control a remote start, much less have the range to make one very usefull.
As for DEI they have been the world leader in car alarms and "remote convenience" systems for several years. Now, while no company is perfect, my personal opinion (after working with them and a few other brands for several years) is that they are tops in the industry. They have a quality product and do a very good job of standing behind it. However, keep in mind that any system is only as good as the guy who installs it... ;)