Water in my gas tank........?

My truck began running horribly a few days ago. It still runs but misses and once in awhile stalls. My dad says this happened due to some ring becoming lose around the gas tank and when it rained water got in. Guess he fixed the ring and added some additives to he gas (he also put in more gas) will this simply fix the problem? I was scared to death of driving over to his house (he lives about 3 miles away). From what I have been reading you need to drain the gas tank first. Just really nervous, him and husband are both working on it, they sound it sounds better but I will need to drive around to let some of the gas burn off? Wouldn't doing that just hurt the engine more? We already replaced the spark plugs and coils so we know its not that. Its a 2001 Ford Ranger 2.5lt 4cyl with about 115,000 miles on it. My dad used to be a mechanic, I am wondering if I should just take it into a shop and have them remove the tainted gas? Thank you for your help!!