Did you ever receive an answer?
This will be my first attempt at winemaking. But, since I'm in Hawaii, and have access to plenty of fresh guavas, I decided to try to make guava wine. Two questions: how much sugar if any? I'm not a fan of sweet wine. And do I keep the seeds or remove them?
I've never made guava wine, but I know others on this forum have. I can speak to your questions from the more generic perspective of making any other fruit wine.
Before adding sugar, you should consider what you want your potential ABV to be in the end. For that, you would measure your juice's specific gravity using a hydrometer prior to adding any yeast. If you anticipate a final gravity (once the yeast has eaten all the sugar) of somewhere between .990 and 1.000 (for the sake of argument, let's say 0.995), then you initial reading will tell you where you're likely to wind up.
If you want something close to 14% ABV, you should have an original gravity of around 1.100. For 12.5%, your original gravity should be around 1.090. Depending on where your gravity is, you may (or may not) need sugar to get your guava must to your desired original gravity.
I'd talk a little about too much sugar here too. Go slow in adding your sugar - I'd do it as simple syrup - until you get to the gravity you want. Also, if you add sugar beyond your yeast's tolerances, you're bound to have a wine that tastes too hot or have residual sugar after your ferment (and instead of dry gauva wine, you wind up with off-dry, semi-sweet or sweet instead).
I'm betting there isn't a ton of sugar in guavas - at least not enough to make a wine that's 10%+. So, adding sugar is pretty likely.
On your other question... Seeds = tannin (body...bitter... pucker... stuff that dries your mouth). They're not a bad thing. The recipes I've seen today include directions to chunk your guavas. So, it seems that seeds are expected. Once you get done fermenting, you'll rack the wine off the gross gauva lees like skins and seeds.
Dig around before you start. Find a recipe that looks interesting to you. The one's I saw added things like brown sugar instead of white, ginger, pineapple, clove, anise, and peppermint...
Good luck!