Works ok when cold but once warm will not shift out of first. Code says shift solenoid valve b. How difficult is this.

 

Assuming that the shift solenoid is the only issue, not too terrible. A bit messy, but pretty straightforward. If you're not familiar with working on the transmission at all, then watch a few videos on YouTube about the procedure. Watch more than one. You get more tips that way.
If you decide to do this yourself, dedicate a day to it. Don't rush. And while you're in there, go ahead and replace all the solenoids, not just the faulty one. You will need a pan gasket and filter kit as well.
Keep the old fluid to put back in when you are done. You will lose a little during this process, but the majority of the old fluid should be put back in. Top off with the correct type of fresh fluid only.
Good luck!

 

A little over 3 years back I lost 1st and 4th gear at the same time. Don't recall what the codes where, but it did say there was solenoid faults. I ended up replacing all of the solenoids as Green said AND the entire wiring harness since the clips have a tendency to snap as you're trying to unplug them when removing them. I bought a kit off eBay I think it was that the seller was putting together with all AC Delco parts, ran me somewhere in the neighborhood of $200; cheaper than a transmission, and much easier and quicker than replacing the entire transmission lol. It's not a terribly difficult job at all, took me maybe an hour, but I also had the benefit of putting the truck on a lift at work. So far the fix is holding up great and I still have the original repaired trans in the truck with 210k miles on it.

Although I can't recommend capturing and reusing the old trans fluid during the process as Green mentioned. If you're going in there, replace the filter AND all of the fluid that drains out (this isn't a full fluid change, there would still be a lot left in the trans and torque converter), but it just doesn't make much since in my opinion to go through all that work just to put old fluid back in it, ATF is cheap...

 

thank you so much too be honest i have absolutely no knowledge of transmissions but i have watched a few videos doesnt look to hard.

 

I had never been into a transmission before I tackled mine either. I had replaced an entire transmission in a Dodge once for a friend but that's it lol. Plenty of work under hoods of various vehicles, including a full engine tare down and rebuild, I'm no stranger to a wrench by any means. But after some reading up I was confident enough to tackle the job, and it was way easier than I was working it up to be in my mind.

 

Allow me to elaborate on the reason to reuse the old fluid.
These trucks are getting old, and chances are that the mileage is high and that the transmission has probably never been serviced, unless you happen to be the original owner and kept it up yourself. There is some amount of friction material in that fluid from your clutch plates. Taking that material away can shorten the remaining life of your already well-used tranny. To be sure, examine the fluid when you take it out. Put it in a transparent container. Then put some new fluid in a separate similar container. Compare the difference. Are there metal flakes in the old fluid? If it sits a while, does there seem to be sediment like material settling on the bottom? Or is it pretty much identical to the fresh fluid?
I've seen many high mileage transmission failures shortly after being serviced.
In any case, proceed with caution and good luck.

 

YEP.... Wanna Kill a High mileage transmission quick do a transmission flush or change out too much of the old fluid

 

The fluid that drained from mine during the process was pretty darn dark, you can see it in the picture that I posted above where it collected in spots as it was dripping. I've probably put 30k on it since then with the new fluid to replace the old stuff that I drained out and it hasn't had a single issue since, but of course that doesn't mean it'll be the same case for everyone I suppose.

Best of luck either way...