I have the DigiQII for my UDS. I put a large BGE vent on my drum so I got the BGE adaptor. Works like a charm. For cheapest way, I would say just get the bulkhead adaptor and you're set.
Step by step:
1. Build a uds
2. Order Guru with bulkhead
3. Install bulkhead
4. Read the manual that comes with the guru
5. Bon Appetite