Help with 3GS

[RLSDR]

I have an Iphone 3GS Model A1303 currently with Firmware 4.1(8B117) & baseband 6.15.00. I moved to the Dominican Republic from the US. AT&T would not unlock, so I tried myself to jailbreak and unlock to use with local carrier. Bad internet connection and something crashed in the jailbreak process. Stuck in recovery loop. Probably my fault cause I am totally new to this. I did not save SHSH's. Did not know they existed till too late. Not even sure what my original firmware was or baseband, no matter now.
I took it to a shop and they got it back working with the firmware and baseband listed above. I do not know what software was used to jailbreak or unlock it.
I need to know how to do this myself. Currently I cannot install iBooks to read pdf's and epub's. Does not work with the currently jailbroken phone. iBooks says it needs a newer version of OS.
Question is, what is the newest firmware version that I can upgrade to, or am I stuck here? Which software to use? (windows) I am looking for an untethered jailbreak. I know that the information is likely on this site, but I have a brain freeze right now from the learning curve.
PS Serial number is 20 indicating old bootrom, but in the original jailbreak process, I ran some software to detect this, and it indicated new bootrom. Currently running usbview.exe it tells me iBoot 359.3.2

Thanks in advance for any help. I am not computer illiterate, just new to the iPhone mess.

[xtacy]

Does Cydia show numbers on top in green?
If you don't have shsh u are stuck for now. Or you can update to 5.0.1 but it will be a tethered one . Wait for some days an untethered jb is around the corner.. :-)

[RLSDR]

Sorry for the delay. Had to wait on a router that would work with my iPhone. Yes Cydia shows in green "SHSH iOS 4.1, 4.3.5, 5.0.1. What options do I have with this? Thanks in advance for the help.

[b0bab0i]

You have to restore a Custom firmware of 5.0.1 using Redsn0w 0.9.10b3

[Susty]

Just so you know (incase your not aware as your new to this) 5.0.1 is now an untethered jailbreak, & with 4.1 you don't need shsh's (apple still sign this) however you'll always need to use custom firmware because you have the iPad 6.15.00 baseband.

[RLSDR]

Thanks to all: It worked. Not perfect, but worked.

[Susty]

Perfect.