Handheld GPS Device Pattern

I'm in the midst of making graduation gifts, and one of my friends is really into geo-caching, so I made him this Handheld GPS Device (the first pattern I've ever written). Here's the original pattern, and if someone wants to change it so that I don't have to cut and tie the yarn every single time I change color, that would be awesome (I don't know how to do intarsia, so perhaps those of you who do won't have this problem).

Materials
Size 9 needles and worsted weight yarn makes a 7"x5" GPS (but change this to suit your preferences)
I used black yarn for the "case" (the thin perimeter on the front and the whole back) and the three smaller "buttons", gray yarn for the "body", white yarn for the "screen," and red yarn for the big "button."
Yarn needle
Small amount of synthetic stuffing

Stitch Patterns
- Knit through the back loop (ktbl)- put your right hand needle into the back of the loop right to left, instead of the usual left to right

- 5 stitch bobble - in 1 loop on left hand needle, k1, k1tbl, k1, k1tbl, k1 (5 stitches), turn work and purl 5, turn work and knit 5, slip sts 2, 3, 4 and 5 over 1 and off right hand needle.

3 stitch bobble - same as 5 stitch bobble but only do "k1, k1tbl, k1" to create three stitches

Pattern
Front
CO 25 stitches
Row 1-4: Knit black
Row 5-12: K2 black, K21back gray, K2 black
Rows 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33: K2 black, K3back gray, K15 white, K3 back gray, K2 black
Rows 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34: K2black, K3back gray, P15 white, K3 back gray, K2 black
Rows 35-39: K2 black, K21back gray, K2 black
Row 40: K2 black, K10 back gray, 5bobble red, K10 back gray, K2 black
Rows 41-43: K2 black, K21back gray, K2 black
Row 44: K2 black, K6 back gray, 4bobble black, K4 back gray, 4bobble black, K6 back gray, K2 black
Rows 45-48: K2 black, K21back gray, K2 black
Row 49: K2 black, K10 back gray, 3bobble black, K10 back gray, K2 black
Rows 50-53 – K2 black, K21back gray, K2 black
Rows 54-58: Knit black

Back
CO 25 stitches in black yarn, and knit 58 rows garter stitch.

Finishing
Sew the two halves together, with a little bit of stuffing to keep it from being flimsy.
Embroider a smiley face on the front screen, and a personal message on the back.