http://www.umd.edu/catalog/index.cfm/show/content.section/c/1/s/103
Here is the CS page from the current course Catalog at UMD. So it looks like if all of your credits from your first degree transfer to UMD you will have the "A minimum of 12 additional credit hours of 300-400 level courses in one discipline outside of computer science with an average grade of C or better." requirement covered.
For the math: "MATH 140 and 141. A STAT course which has MATH 141 (or a more advanced mathematics course) as a prerequisite, and one other MATH, STAT, or AMSC course which has MATH 141 (or a more advanced mathematics course as a prerequisite. A grade of C or better must be earned in each of the courses. No course that is cross-listed as CMSC may be counted in this requirement.". That is where a junior/community college might come in handy. You would have to check what transfers, but it might be posible.
After that stuff (and the core requirements for a degree from UMD. Hopefully you will already have that covered w/ transfers) you have 39 credit hours of computer science.
http://www.umd.edu/catalog/index.cfm/show/content.section/c/2/s/231
This page has additional requirements for the college the CS department is in. It says you have to do your last 30 hours in residence, so you'd have to get the community college done at the very beginning or before you even start.
I looked at the schedule/catalog and came up with this. A line with a - means it's a pre-req for the class listed above it. The lines with | mean only one of the courses in that group with the | may be taken. Note that 131,132,212, and 250 are implicit requirements since they are pre-reqs to 311/330/351 or one another. These are not mentioned in the requirements for a degree, so you may be able to get credit for those via exam, transfer, AP, etc. Not sure what of those are viable for you now, but it might be a way to get a jump start.
Required:
CSMC 131
-MATH 140
CSMC 132
-CSMC 131
CSMC 212
-CSMC 132
CSMC 250
-CSMC 131
CSMC 311
-CSMC 212
-CSMC 250
CSMC 330
-CSMC 212
-CSMC 250
CSMC 351
-CSMC 212
-CSMC 250
- - - - -
Choose from 18 hours of the following:
CSMC 411
-CSMC 311
CSMC 412
-CSMC 311
-CSMC 330
CSMC 414
-CSMC 311
-CSMC 330
CSMC 417
-CSMC 351
-CSMC 311
CSMC 420
-CSMC 330
-CSMC 351
|CSMC 421
-CSMC 330
-CSMC 351
|CSMC 424
-CSMC 420
|CSMC 426
-CSMC 420
|CSMC 427
-MATH 240
-CSMC 420
CSMC 430
-CSMC 330
CSMC 433
-CSMC 330
CSMC 434
-CSMC 330
CSMC 435
-CSMC 412 or 417 or 420 or 430 or 433
CSMC 451
-CSMC 351
|CSMC 452
-CSMC 351
|CSMC 456
-Two 400 level math classes
-CMSC 106 or 114
-Permission of dept.
|CSMC 460
-MATH 240
-MATH 241
-CMSC 106 or 114
-Permission of dept.
|CSMC 466
-MATH 240
-MATH 241
-CSMC 106 or 114
-Permission of dept.
Semester 1:
CSMC 131
Semester 2:
CSMC 132
CSMC 250
Semester 3:
CSMC 212
Semester 4:
CSMC 311
CSMC 330
CSMC 351
Semester 5:
3 Upper division
Semester 6:
3 upper division
You might be able to push a few of the upper division things that require 311 and/or 330 and/or 351 into the same semester as those as co-reqs instead of pre-reqs, but that will be at the discretion of your advisor or the dean of the school. If you could push 212 as a co-req with 132, that would cut a semester out. So essentially you're down to 4-5 semesters. Maybe 1-2 could be summer semesters. If you did take some math at UMD that could fill in some of the first few semesters where you can't do too much CS b/c of pre-reqs. I will add that I did 3 upper division CS courses a semester towards the end and it was devastating, so don't plan on doing much else those semesters, and if you get a few knocked back and want to try 4... just... plan to lock yourself in a room whenever you aren't in lectures.
I guess another option is a Master's in CS. You'd probably need to take some of these classes to get a foundation, but it may take you about the same amount of time. You already have a bachelor's, so a graduate degree might make more sense.
For getting started with C, I would just google for a tutorial and "Hello, World!" example to start out with. Use the terminal and gcc. There will be no XCode in college. Once you've gotten your feet wet, I would buy "The C Programming Language" by Kernighan and Ritche. It is the best reference you can buy. Then start thinking of problems you want to solve, and try to solve them.
Good luck.
-Lee