1) The screen is very small is there anyway to hook it up to a monitor? If so what cable should I use?
It comes with a VGA port, yes you could attach it to an external monitor.
2) Does OSX on a dell mini 10v work well or does it freeze up and work really slow?
Well I wouldn't call it very smooth but it's fine, depends what you use it for, there could be some slowdown or none at all. For me the major slowdown come from browsing complex web pages, some web sites these days really aren't very suitable for netbooks.
3) One reason I want a mac is to make iPhone apps. Will I be able to make iPhone apps with this laptop.
The short answer is yes, you can do iPhone development on it. Xcode is totally fine, Interface Builder is usable but you need to move windows around since the screen can't handle all of them at once, iPhone simulator is...well not that great, you will have to use the 50% scale which it defaults to, or use 100% but drag it around since you can't see all of it in portrait mode.
4) Will i be able to hook up a wireless mouse with this laptop. If so should I use a mac or pc mouse.
Any pc or mac mouse should be fine, I use a 2.4Ghz wireless pc mouse and it works fine, no additional driver required.
5) Is there any other information I should know before buying/hackintoshing a dell mini 10v?
Now it comes down to very personal opinions of mine. I say DO NOT buy it unless if you're really short on budget or just want to give the Mac and iPhone development thing a try without being serious on them.
I really hate to be overreacting but dell 10v is the worst piece of crap I've every used as a laptop/netbook, if it wasn't for Snow leopard that runs perfect on it I would slap myself for buying such a useless computer. The whole designing/manufacturing of the case feels very cheap, as if it was made by one of those Shanzhan/KIRF manufacturers in China. The screen is bad, really bad, if you see it side-by-side with a Samsung NC10 you will know what I mean. The touchpad is absolutely crap, hence you will need a mouse for it to be usable. I've used netbooks like Lenovo S10 and Samsung NC10, but this one doesn't even come close to the quality of them.
Sorry for the above whineage, that's really not the point I was trying to make, my point is, even though Snow Leopard runs great on a dell 10v, it's still far from the quality of a real Mac. If you're short on budget I say give the Mac Minis a try, they are not in high specs but at least they will perform better than a netbook. And if you are not, a 15-inch Macbook Pro will not only give you the best experience as a Mac, but also more comfortable for your eyes and your development works.