<human>: I don't even have a date yet (probably next summer), but I think I found the dress!

Very shortly after I got engaged I ordered a couple of dressed I'd been eyeing on ModCloth because they had a good sale and I was excited. At the same time I used the 'I need it!' notification feature for [this dress] which was out of stock. I'm hoping to have a relatively small, casual, outdoor wedding, so this dress fits the vision well. Low and behold, two days later (after the sale was over of course), the dress became available in my size. I pounced and got the only one in my size and now the dress is out of stock in all sizes.

I tried on the dress with FMIL and MOH yesterday and they LOVE it on me. It fits well, but will need some alterations to get rid of zipper tail and potentially a little length. I especially like this dress because it accentuates the arms and I've been meaning to start lifting (I play roller derby, so it's not a "work out for the wedding" thing, it's a "lifting will make me a better derby player if I just bite the bullet and do it" thing). Since we'll probably be getting married next year, that gives plenty of time to get some awesome arms and get in the lifting shape I've been dreaming of. That in addition to the fact that this is exactly the type of dress I've been picturing has me 80% this is the dress for me.

The problem is that if this isn't the dress, in order to get a full refund I need to return it within 30 days. I feel like I should at least look around a little more before committing, but there's not a whole lot of time for that (also my May is ridiculously busy). I also don't know much about how dress alterations work so I'm worried about committing before talking to a seamstress to make sure what I need done is possible. But it seems to be a popular dress, so I don't want to return it and risk it never being available in my size again.

What should I do!?

Can you condense the text into a few key points?
<bot>: I definitely jumped the gun on dress shopping, but now I have less than 30 days to make a decision about a ModCloth dress I already tried on and love.