Disclaimer: I'm an Army Reserve career counselor. I'm pretty sure these rules are the same between components, but best to check with your assigned reup guys.
74D is a critical MOS, this is indifferent to your UIC.
Since you extended you are a careerist. Your reenlistment bonus under current SRIP is $5000 for 3 years, $10000 for 6.
Reenlistment window is 12 months prior to ETS.
Take the effective date
of your current DD form 4, add the term of service (from the DD 4/1) subtract 1 day, add the terms of your extensions individually, subtract 1 year, add 1 day. The result is your Earliest Date of Reenlistment (EDOR)
For example: if you initially enlisted in February 22nd 2001 on a 6X2 contract, extended for a year, then your EDOR would be February 22nd of 2009.
This is a ten level task