Help with Joomla 1.5 and CB Subscriptions

Hello
I run a Web site for a horse breed society. The site is on Joomla 1.5 and has CB Subscriptions installed. The installation was done by programmers; most of the rest of the site was set up by me.
I’m having some problems with the site which I would like fixed:
• There are many (600+) registered users of the Web site. I wish to allow them to join the breed society by entering their contact details and paying a fee. Joining the society works fine for people who are not already registered on the site but it won’t let registered users join and currently doesn’t offer them the opportunity to upgrade to being a paying user
• The front end login is buggy – when I attempt to login it simply redirects me to the login page in a loop. The problem started in IE and has spread to Firefox
• I can’t “find” one of my login IDs on the back end
I will need a firm estimate of the cost to fix these jobs before they are undertaken.
I would also like to build a relationship with a Joomla programmer for future projects. The person who undertakes these jobs must have good communication skills i.e. be able to tell me when they are going to work on the problem, when they have fixed it and, if appropriate, what they have done to apply the fix. (If “proper” programming is involved that won’t be necessary as there’s no way I’ll be able to duplicate it myself). Ideally I would like some guidance on what else we could achieve on the site.

Thank you