I don't think it will be a huge problem, although credit unions are more picky than banks in approving credit cards in my experience. As far as your credit record goes, the WF account should just show up as closed, but not delinquent - you don't want a lot of closed accounts, but as long as you weren't late on payments it should look the same as if you closed the account. It will hurt your credit score a little, because now you're using more of your total available credit, but unless you've recently checked your credit score before this happened it's hard to see how much that was affected.
Your WF credit card was probably closed because you didn't use it very much. You were totally responsible about your personal finances, but banks have been closing inactive credit card accounts a lot the last few years - even for long-time customers with perfect credit. Banks generally don't give any notice before they do this - I would say protosaurus' example is an exception. It's a decision made by an algorithm, and whoever told you it was due to "mismanagement of other accounts" probably had nothing to do with the decision, and just wanted to get you off the phone.
If you do get another credit card, and you're not carrying a balance, you need to charge something at least once every month or two, and then pay off your balance monthly so you don't get charged interest. That way you're showing activity, and the lender is making a little money on the transaction fees. It also will look good on your credit. It doesn't have to be a lot - maybe $10 - $25 a month, something you would normally pay cash for. If for whatever reason you don't want to use the credit card like this, you might want to apply for a line of credit with your credit union - it's unsecured credit like a credit card, but is intended to be used as a safety net, like if you overdrew your checking account. You should definitely ask what happens in case of fraud, like if someone got access to your accounts - I think credit card accounts have more consumer protection for fraudulent charges than a line of credit account.
It's a good idea to check your credit before applying - you get a free report from each of the three credit bureaus once a year through annualcreditreport.com. (How to read your credit report at about.com is helpful for interpreting your report.) If you want to check your credit score, don't waste time paying for anything except your official FICO score - this is the score used by most lenders, and you can only get it at myfico.com. You can get it free with a credit monitoring trial, but don't forget to cancel the program before you get charged. You can get a rough idea of your FICO score for free through Credit Karma - they have a lot of helpful information about improving your credit, but they don't use the official FICO score. About.com has some info about how to Check your credit score online.
When you apply for credit, it probably doesn't matter whether you do it online or in person - it all goes through a program, and there's no opportunity to explain the circumstances. When I first joined BECU I applied for a credit card in person, and was denied; I got a letter with the reasons why, including an old delinquent account that was still on my credit report, and a phone number of a credit specialist at BECU I could call. I thought it was weird because I had a few credit cards from banks with great payment records for at least a couple of years at the time. I didn't bother calling, and then about a year later I was offered a line of credit with BECU and eventually a BECU Visa. They definitely pay attention to credit improvements.
It sounds like you've got a great recent credit history; I would be more worried about the past collection, because that will still show up. Make sure that it it shows up as paid on your credit reports - if it doesn't, get that fixed before applying with your credit union. If you do get denied, try calling and talking with the credit or loan specialist and see if they can help you. If you still get denied, try again in a year, or maybe apply for a credit card with a traditional bank.
I hope you are saving for emergencies - it's much better to have at least 6 months of living expenses saved up as a safety net instead of using credit cards. Even if you can't save very much at a time, save something every paycheck & keep it in a separate account, like an online savings account, if you're tempted to spend it. Once you save at least 6 months of total living expenses, keep saving & transfer money every once in awhile into another savings account fund for something like a dream vacation or health/dental expenses.