Internally grounded just means there is no wire for the ground....bolting it to the frame is grounding it.
For power the jack connects to the positive terminal on the battery - so to me it doesn't sound like you did anything wrong.
When you get the new fuse-holder (Walmart sells one, but it does not have a cap to protect from the weather....auto parts stores carry one just like it, but it has a cap cover). It should be a mini-ATC fuse holder rated for at least 30 AMPS. Something like this:
http://www.radioshack.com/product/in...entPage=family
You may also want to get a volt meter or multi-meter to test voltage/continuity, etc.
I was having trouble with my exterior patio lights and ended up getting a digital multi-meter this weekend at Lowes to troubleshoot (turned out my switches were acting up....probably from the previous wash).
I bought a good digital meter at Lowes. I'd stay away from the $10 Wal-Mart meters. The meter is an essential tool in toubleshooting any electrical problems.
The meter can also be used to test fuses, or often times the variety fuse pack's sold at most hardware/auto stores include a fuse tester.
The jack may not have worked for a few reasons:
1) if you have a 75Amp fuse like I do between 6 volt batteries and that blew, you would only be getting power from one battery (6 volts), not enough to power the jack)
2) The jack itself blew a fuse - did it have an in-line fuse or a fuse under the housing?
3) You don't have a good ground connection for the jack. As mentioned they are grounded when you bolt it to the frame. I've heard of people having to scrape away paint to make sure there is good metal on metal contact....also if you have a swing hitch, you may have to run a jumper wire from one of the 3 jack bolts to the other side of the a-frame to get a better, more constant ground connection (even though my jack is in the mail, I've already run a jumper wire because I have a swing hitch and have read about ground issues).