Just bought an iPhone 4...can someone clarify some things for me?

[jbdc41]

This is my first iPhone since the original 2G, and after spending all day tinkering with jailbreaking and unlocking, I'm at the end of my rope. It has gotten so complicated. I have three areas which I am absolutely confused on, and they are in regards to the stability of the unlock (ultrasn0w), fixing MMS and Push Notifications, and upgrading to 4.2.1. But first, here are the facts:

iPhone 4 running 4.0.2 and the 1.59.00 baseband
SHSH saved in TinyUmbrella (Apparently for 4.3, which confuses me)
I'm using OS X 10.6.6 and iTunes 10.2.1.

The Unlock
The issue that I'm having here is that after installing usn0w 1.2, the unlock doesn't seem consistent. I'll have full service one minute, but after installing a package from Cydia, I lose service. I get one bar, no carrier name, and the "carrier" menu option from settings disappears. Also, no calls or texts go through. Any ideas? To be more specific about the packages, they have to do with:

My MMS and Push Issues
I know there have been a million threads regarding this issue, and believe me I've looked through a lot of them, but I'm still having trouble getting MMS going. I tried two packages, the first is from leimobile's repo. This one was called something like "MMS Fix for T-Mobile" and it did nothing. The second had a similar, if not the same, name and was from Pushfix's repo. From what I remember, this one was able to give me the camera icon and network settings tab. From there I made sure all of the correct info was there but I still cannot send or receive MMS.

As far as Push, I used to use a program called Push Doctor to fix my 2G's push woes. It was a good, free alternative to Push Fix. Has that changed at all? Is Push Fix the only game in town? Should I be worried about using it with the above issues?

Upgrading and Restoring
Out of my frustration with these other issues, I decided to see if upgrading to 4.2.1 would help with these things. I found a guide online that walked you through using TinyUmbrella to upgrade an iPhone 4 while leaving the baseband alone. I ended up in a real bad spot with my phone stuck in DFU and drowning in 1600 errors. I managed to get out of that though.

Am I correct in assuming that because I only have a 4.3 SHSH on TU, I'll only be able to upgrade to 4.3 when the jailbreak is out for that? Would I be able to upgrade and maintain my baseband using the same method? Also, is there no way to restore to a 4.0.2 install if something goes wrong?

If you've read this far, thanks so much. Information on this is really overwhelming when you come into the game as late as I did. Especially since it seems like a good deal of the published info is outdated and not updated when Apple stops signing older SHSHs.

[Goof]

1) What I would do is update the iPhone to iOS 4.2.1 and preserve the Baseband. To Do this follow the Step-by-Step guide here:
How to Preserve Baseband, Jailbreak, Unlock iPhone 4, 3GS, 3G on 4.2.1 Using PwnageTool 4.2 / Sn0wbreeze 2.2 [Video] | Redmond Pie


2) Here is an MMS fix that has been known to work
Fix T-Mobile US MMS Problem on iPhone 4 on iOS 4.0.1 / 4.0 | Redmond Pie

3) You cannot keep your Baseband if you upgrade to 4.3, and there isn't an official tool out yet for a 4.3 jailbreak. DO NOT UPGRADE

[jbdc41]

Thanks for the help, I did run into some more roadblocks though. First, after going through the process of creating a custom firmware with Pwnagetool 4.2, iTunes tells me that my iPhone isn't eligible for the requested build. Meaning they've stopped signing for 4.2.1 right? Which means I need a 4.2.1. SHSH stored in order to restore to that firmware? When I try to save my SHSH on TinyUmbrella, I can only save a 4.3 SHSH. Is that supposed to happen?

Am I stuck with 4.0.2 until a untethered jailbreak comes out for 4.3 as well as either a way to preserve the baseband or a new ultrasn0w come out?