Sheesh, this stuff can get confusing - I need to undo a Jailbreak, Help Please

Hi members,
i get the feeling i am about to get in to some serious trouble if i have a go at this restore routine. i have checked out a bunch of posts & discovering all about shsh, basebands, tiny umbrellas & even colored poisons. so here is my situation, a simple one for you guys, headache for me.
I have iPhone 4 4.2.1. Base band 3.10.01. Curiosity got me to jailbreak. did that with greenpoison. worked without fault.
i have decided that i want to undo the jailbreak. the search begins. the only thing i have done so far is dl tinyumbrella & save my shsh. it saved iOS 4.3.5.
OK, so what do i do now? i just want to get out of the jailbreak and back to Apple settings. i dont really care which software version, the latest will do. it doesnt really matter to me. If i connect to iTunes and simply click update to 'latest software version', will that do it? Or do i need to prepare something in advance to avoid a lot of the failures that lots of people seem to be getting.
I thank you in advance peeps, this forum is brilliant.
regards

update: well, while waiting for a reply, I read somewhere in the forums that just a classic restore & update with iTunes would do the trick. I confirmed this by reading an article by Mac Life titled ' How to Undo a Jailbreak'.
Fell for it hook line an sinker!
iTunes failed & returned a 1013 error. Just brilliant. Still connected to iTunes and it tells me that iPhone is in recovery mode.
I would appreciate some guidance on this. i have read a bunch of posts and they all seem a little different from one another depending on version & states.
I would really appreciate any help on this.
Thanks all

If all you're attempting to do is restore to 4.3.5, then the post saying to restore the stock firmware should be correct. You can get a 1013 if you have improperly modified your hosts file (or let a program such as TinyUmbrella modify your hosts file). Navigate to your hosts file (different locations on mac/pc) and then comment out any lines that say "gs.apple.com" by putting a # in front of them. You should then be able to restore to 4.3.5 successfully. This has nothing to do with the jailbreak specifically, and more to do with changes made on your system by previous jailbreaking attempts.