From the post I see you're hired as a sysadmin and it sounds like the additional duty of training other IT staff.
What you can do will depend on where you are in the chain, if there's an IT manager and/or C position above you then you can only go so far. (Unless they're asking you to do their job.) As a sysadmin you have to focus on the servers and network IMHO. And in that regard I agree with several of the posters about going virtual. Ideally you need to store the VM's on a SAN of some type and plan your load so if some of the physical servers fail you can move the VM's around.
I read thru a bunch of comments but did anyone ask if there's a security person on the team? Will you have to plan physical and digital security for this upgrade? Because that's a whole other bag of cats. Because changing from default passwords is one thing but having a plan to update every 6 to 12 months, where will they be recorded, and all the fun of creating access groups.
If you have to upgrade the desktop side I'll give you two scenarios from my last 2 jobs.
Company A) Purchases 4 years complete care from Dell. Without knowing numbers I know this is expensive but if anything happens I know all my PC's will be back up the next day even if the end user dropped the PC down the stairs. This org. purchased enough PC's to replace 1/4 one year, the following they purchased 2/4 more PC's to replace all that were running out of warranty.
Company B) They purchased 3 year standard warranty on all PC's. Now here's the interesting thing. We performed an annual refresh in which we replaced 25% of the employees PC's. The only downside to this plan is we had 4-5 models of PC's and our image ended up having drivers for 10 models when you count desktops, laptops and precision workstations. And if anyone broke their PC between years 3-4 we had to refresh out of band so we had to have PC's on hand in supply. The advantage though is obvious, you balance the cost of the refresh and it runs as a continuous part of the IT budget instead of running the worry of being pushed off because THIS year wasn't so good for business.
As far as training goes, well, I'm the tech that has to know WHY something works the way it does. So I usually end up annoying the teacher because I inevitably end up asking questions they cannot answer and then I have to figure out via the google gods (why can't I hard set 'Verbatim'?)
I think the biggest problem you'll have with training is if you have techs who like the way the company runs now and don't want the extra work because they're going to fight you every step and/or do stuff half-assed. The best you can do is DOCUMENT. Figure out how things need to be and write the process/details and any tech who cares and wants to be there will be able to follow you.
That's my 2 warped cents.