We're almost at the end of renovating our house, started over a year ago, some carpets and bits & pieces left to do. I was always thinking of the The Money Pit too (love that film).
It was a total nightmare, first thing I would recommend is do not live there at the same time. We did and it was so stressful, my BF and I were arguing all the time. At one point we had no toilet or running water, there was a huge hole in one outside wall, it was snowing, I was living and sleeping in one room and my BF chose that time to go on a length business trip. I'm struggling to think of a more miserable time.
The other thing I'd recommend if you can is to get a Project Manager to oversee the whole thing. It takes up so much time getting quotes and arranging to meet people at the house, it really is a full time job. If you're doing it yourself and you work then I hope you have an understanding boss as you'll need a lot of time off.
Then on to budget, we didn't have one and it was a big mistake, I don't know what the final spend will be and I don't want to know. Luckily house prices are still going up and I think we'll be ok.
Good Luck.