A couple things...
1) By definition, a 403(b) account is an employer sponsored plan, and not an individual plan
2) You can set up a plan that only involves you, that is to say, a single account in your name, but you'll need your employer's help.
3) At a minimum the church will need to withhold your contribution and forward it to your mutual fund provider of choice.
4) Our church has set this up with Vanguard, they require a minimum amount of $5000 per person, only one person in your case. I believe T. Rowe Price can also set up.
5) Vanguard can send you an employers guide and an employee's guide that will give you more information.
6) I believe that Vanguard will provide you with a salary deferral agreement, a deferall form, and a plan document that you can adopt.
You can get the forms at this address (try copying and pasting int the browser: http://flagship5.vanguard.com/VGApp/hnw/LiteratureRequest?FW_Activity=FindLiteratureActivity&FW_Event=subcategory&cat_cd=OPEN&sub_cat_cd=NPRP&entryPoint=ELF&usage_cat=OPENNPRP&active_menu_item=CBD_NON_PROFIT_RETIREMENT_PLANS
Hope this get's you started - God bless!