Your iPad comes with a 1 year limited hardware warrantee from Apple. Doesn't matter where it was purchased from. If it turns out to be a hardware problem, it's covered. The 90 days is only for free tech support.
Sounds like the 3 year coverage you got from Sam's Club may be the Apple Protection plan. If it is then you also have 3 years of tech support from Apple. Check your plan.
Since you are uncomfortable doing the restore yourself, use Apple's tech support if it turns out you do have the coverage.
Restoring your iPad will have no effect on the other iPad. iTunes is smart enough to know they are different devices.
Save all important files off the iPad before restoring. You may be able to recover them with a restore from backup afterwards, but don't take a chance. Before you restore, make sure you get a good backup in iTunes. This will give you the best chance of getting your iPad back in order with the minimum of fuss.
Backing up in iTunes is easy. It does one every time you sync. Before you do the last backup, right click on the iPad in iTunes and choose Transfer Purchases. You can force a backup the same way.
When you are ready and sure all you important files are saved either in iTunes or elsewhere, all you have to do to restore is choose Restore from the summary page. When it is finished your iPad will look exactly like it did when it came out of the box.
When you connect the iPad to iTunes after the restore it will want to set it up again. It should offer you a chance to restore from a backup, just like it did when you set your husband's up. Choose your backup and let it do its thing. Before you sync, go through all the sync pages and make sure they are setup the way you want.
You may end up having to do some minor tweaks to get everything back, but most of it should be fine.