I agree a 5hp engine is a little wimpy a 9.9 would be more like it. A lot had to do with your sailing conditions, if you sail in an area with strong currents and high winds you'll probably need more hp. My suggestion is to give the current engine a try and keep your eye out for a used 9.9. You'll often see bargains on e-bay or local paper.
If your main is the original it's probably blown out. If the fabric is OK, it might be able to be reconditioned. I've read some very good things about Sail Care 800-433-7245
http://www.sailcare.com/ but have not used them myself. Before you buy new sails have them evaluated by Sail Care. Worst case they'll say it is not worth reconditioning and you'll be out the mailing costs.
If SailCare can't recondition yours you can get a price on a new one or a good used sail. If they have your old one it will be easier to match it to your requirements. It's important that the actual luff, leech and foot measurements be available when shopping for sails - Don't rely on the I, J, P & E measurements listed in Hunter's literature.
Then check a few other companies that sell sails as a basis of comparison with Sail Care. Practical Sailor did a review of sail retailers in March 2005 and listed these companies as being good sources.
Sail Exchange 800-628-8152
http://www.sailexchange.com
National Sail Supply 239.693.1896
http://www.nationalsail.com
Cruising Direct 888.424.7388
http://www.cruisingdirect.com
Far East Sails 206.339.3618
http://www.fareastsails.com
The Sail Warehouse 831.646.5346
http://www.thesailwarehouse.com
Air Force Sails 877.237.2457
http://www.airforcesails.com
Once you have the Luff, Leech and Foot measurements call a couple of these companies for prices so you can compare against the Sail Care price.
National Sail Supply got the nod from Practical Sailor for offering the best price and by far the most attentive responses. As far as used sails go, PS gave the nod to the Sail Exchange.
A recent discussion on sail vendors on hunterowners.com indicates Atlantic Sail Traders got very high marks from former customers.
http://www.usedsails.com/ 1-800-946-3800